bipeds (Chirotes and Pseudopus), (4) serpents,—an arrangement in which the old confusion of Batrachians and reptiles and the imperfect definition of lizards and snakes are continued, and which it is worthy of remark we find also adopted in Cuvier's Tableau élémentaire de l'histoire naturelle des animaux (1798), and nearly so by Latreille in his Histoire naturelle des reptiles (Paris, 1801, 4 vols. 12mo). Lacépède's monograph, however, remained for many years deservedly the standard work on reptiles. The numerous plates with which the work is illustrated are, for the time, well drawn, and the majority readily recognizable. Brong 3. The Period of Elimination of Batrachians as one of the Reptilian Orders.-A new period for herpetology commences with Alex. Brongniart, who in 1799 first recognized niart. the characters by which Batrachians differ from the other reptiles, and by which they form a natural passage to the class of fishes. Caecilia (as also Langaha and Acrochordus) is left by Brongniart with hesitation in the order of snakes, but newts and salamanders henceforth are no more classed with lizards. He leaves the Batrachians, however, in the class of reptiles, as the fourth order. The first order comprises the Chelonians, the second the Saurians (including crocodiles and lizards), the third the Ophidians-terms which have been adopted by all succeeding naturalists. Here, however, Brongniart's merit on the classification of reptiles ends, the definition and disposition of the genera remaining much the same as in the works of his predecessors. The activity in France in the field of natural science was at this period, in spite of the political disturbances, so great that only a few years after Lacépède's work another, almost Daudin. identical in scope and of the same extent, appeared, viz. the Histoire naturelle générale et particulière des reptiles of F. M. Daudin (Paris, 1802-3, 8 vols. 8vo). Written and illustrated with less care than that by Lacépède, it is of greater importance to the herpetologists of the present day, as it contains a considerable number of generic and specific forms described for the first time. Indeed, at the end of the work, the author states that he has examined more than eleven hundred specimens, belonging to five hundred and seventeen species, all of which he has described from nature. The system adopted is that of Brongniart, the genera are well defined, but ill arranged; it is, however, noteworthy that Caecilia takes now its place at the end of the Ophidians, and nearest to the succeeding order of Batrachians. The next step in the development of the herpetological system was the natural arrangement of the genera. This involved a stupendous amount of labour. Although many isolated contributions were made by various workers, this task could be successfully undertaken and completed in the Paris Museum only, in which, besides Seba's and Lacépède's collections, many other herpetological treasures from other museums had been deposited by the victorious generals of the empire, and to which, through Cuvier's reputation, objects from every part of the world were attracted in a voluntary manner. The men who Oppel and Cuvier. devoted themselves to this task were A. M. C. Duméril, Duméril, Oppel and Cuvier himself. Oppel was a German who, during his visit to Paris (1807-1808), attended the lectures of Duméril and Cuvier, and at the same time studied the materials to which access was given to him by the latter in the most liberal manner. Duméril 2 maintains that Oppel's ideas and information were entirely derived from his lectures, and that Oppel himself avows this to be the case. The passage, however, to which he refers is somewhat ambiguous, and it is certain that there is the greatest possible difference between the arrangement published by Duméril in 1806 (Zoologie Analytique, Paris, 8vo) and that proposed by Oppel in his Ordnungen, Familien, und Gattungen der Reptilien (Munich, 1811, 4to). There is no doubt that Oppel profited largely by the teaching of Duméril; but, on the other hand, there is sufficient internal evidence in the works of both authors, not only that Oppel worked independently, but also that Duméril and Cuvier owed much to their younger fellow-labourer, as Cuvier himself indeed acknowledges more than once. Oppel's classification may be shortly indicated thus:- Sect. A. SAURII. Fam. I. CROCODILINI (gen. Crocodilus, Gavialis, Alligator). Fam. 4. LACERTINI (gen. Tupinambis, Dracaena, Lacerta, Tachydromus). Fam. 5. SCINCOIDES (gen. Scincus, Seps, Scheltopusik, Anguis). Fam. I. ANGUIFORMES (gen. Tortrix, Amphisbaena, Typhlops). Fam. 3. HYDRI (gen. Platurus, Hydrophis). Fam. 4. PSEUDO-VIPERAE (gen. Acrochordus, Erpeton). ORDER 3. NUDA OR BATRACII. In this classification we notice three points, which indicate a decided progress towards a natural system. (1) The four orders proposed by Brongniart are no more considered cosubordinate in the class, but the Saurians and Ophidians are associated as sections of the same order, a view held by Aristotle but abandoned by all following naturalists. The distinction between lizards and snakes is carried out in so precise a manner that one genus only, Amphisbaena, is wrongly placed. (2) The true reptiles have now been entirely divested of all heterogeneous elements by relegating positively Caecilia to the Batrachians, a view for which Oppel had been fully prepared by Duméril, who pointed out in 1807 that "les cécilies se rapprochent considerablement des batraciens auxquels elles semblent lier l'ordre entier des serpens." 4 (3) An attempt is made at arranging the genera into families, some of which are still retained at the present day. In thus giving a well-merited prominence to Oppel's labours we are far from wishing to detract from the influence exercised by the master spirit of this period, Cuvier. Without his guidance Oppel probably never would have found a place among the promoters of herpetological science. But Cuvier's principal researches on reptiles were incidental or formed part of some more general plan; Oppel concentrated his on this class only. Cuvier adopts the four orders of reptiles proposed by Brongniart as equivalent elements of the class, and restores the blindworms and allied lizards and, what is worse, also the Caecilias, to the Ophidians. The chameleons and geckos are placed in separate groups, and the mode of dividing the latter has been retained to the present day. Also a natural division of the snakes, although the foreign elements mentioned are admitted into the order, is sufficiently indicated by his arrangement of the vrais serpens proprement dits" as (1) non-venomous snakes, (2) venomous snakes with several maxillary teeth, and (3) venomous snakes with isolated poison-fangs. He distinguishes the species of reptiles with a precision not attained in any previous work. Cuvier's researches into the osteology of reptiles had also the object of discovering the means of understanding the fossil remains which now claimed the attention of French, English and German naturalists. Extinct Chelonian and Crocodilian Memoires de zoologie et d'anatomie comparée (Paris, 1807, 8vo), P. 45. remains, Pterodactylus, Mosasaurus, Iguanodon, Ichthyosaurus, Teleosaurus, became the subjects of Cuvier's classical treatises, which form the contents of the 5th volume (part 2) of his · Recherches sur les ossemens fossiles, où l'on rétablit les caractères des plusieurs animaux dont les révolutions du globe ont détruit les espèces (new ed., Paris, 1824, 4to). Blain All the succeeding herpetologists adopted either Oppel's or Cuvier's view as to the number of orders of reptiles, or as to the position Batrachians ought to take in their relation ville. to reptiles proper, with the single exception of D. DE BLAINVILLE. He divided the "oviparous subtype" of Vertebrates into four classes, Birds, Reptiles, Amphibians and Fishes,1 a modification of the system which is all the more significant as he designates the reptiles "Squammifères Ornithoides, écailleux," and the amphibians "Nudipellifères, Ichthyoides nus." In these terms we perceive clear indications of the relations which exist to the class of birds on the one hand, and to that of fishes on the other; but, unfortunately, Blainville himself did not follow up the ideas thus expressed, and abandoned even the terms in a later edition of his systematic tables. The direct or indirect influence of the work of French anatomists manifested itself in the systems of the other herpetologists of this period. The Crocodiles, especially, which hitherto (strange to say, even in Cuvier's classification) had been placed as one of the families of Saurians, now commence to be separated from them. MERREM (Versuch eines Systems der Amphibien, Marburg, 1820, 8vo) distinguishes two classes of "Amphibians," Pholidota and Batrachia. Merrem. Latreille. LATREILLE, who commenced the study of reptiles as early as 1801, had kept pace with the progress of science when he published, in 1825, his Familles naturelles du règne animal (Paris, 1825, 8vo). He separated the Batrachians as a class from the Reptiles, and the latter he divides into two sections only, Cataphracta and Squamosa-in the former Crocodiles being associated with the Chelonians. He bases this view on the development of a carapace in both, on the structure of the feet, on the fixed quadrate bone, on the single organ of copulation. None of the succeeding herpetologists adopted a combination founded on such important characters Gray. except J. E. GRAY, who, however, destroyed Latreille's idea of Cataphracta by adding the Amphisbaenians 2 as a third order. A mass of new materials now began to accumulate from all parts of the world in European museums. Among others, Spix had brought from Brazil a rich spoil to the Munich Museum, and the Bavarian Academy charged JOH. WAGLER Wagler. to prepare a general system of reptiles and batra chians. 3 His work, the result of ten years' labour, is a simple but lasting monument to a young naturalist, who, endowed with an ardent imagination, only too frequently misinterpreted the evidence of facts, or forced it into the service of preconceived ideas. Cuvier had drawn attention to certain resemblances in 1 Bull. Sci. Soc. Philomat., July 1816. Catalogue of the Tortoises, Crocodiles and Amphisbaenians in the Collection of the British Museum (London, 1844, 16mo), p. 2. 3 Natürliches System der Amphibien mit vorangehender Classification der Säugethiere und Vögel-ein Beitrag zur vergleichenden Zoologie (Munich, 1830, 8vo). Wagler was accidentally killed three years after the publication of his System. some parts of the osseous structure of Ichthyosaurus and Pterodactylus to dolphins, birds, crocodiles, &c. Wagler, seizing upon such analogical resemblances, separated those extinct Saurians from the class of Reptiles, and formed of them and the Monotremes a distinct class of Vertebrates, intermediate between mammals and birds, which he called Gryphi. We must admit that he made free use of his imagination by defining his class of Gryphi as vertebrates with lungs lying free in the pectoral cavity; oviparous development of the embryo (within or) without the parent; the young fed (or suckled ?) by the parents.' By the last character this Waglerian class is distinguished from the reptiles. Reptiles (in which Wagler includes Batrachians) are divided into eight orders: Testudines, Crocodili, Lacertae, Serpentes, Angues, Caeciliae, Ranae and Ichthyodi. He has great merit in having employed, for the subdivision of the families of lizards, the structure of the tongue and the mode of insertion of the teeth in the jaws. On the other hand, Wagler entirely failed in arranging snakes in natural families, venomous and non-venomous types being mixed in the majority of his groups. L. FITZINGER was Wagler's contemporary; his first work 5 preceded Wagler's system by four years. As he says in the preface, his object was to arrange the reptiles in Fitz a natural system." Unfortunately, in order to inger. attain this object, Fitzinger paid regard to the most superficial points of resemblance; and in the tabula affinitatum generum which he constructed to demonstrate "the progress of nature" he has been much more successful in placing closely allied generic forms in contiguity than in tracing the relationships of the higher groups. That table is prepared in the form of a genealogical tree, but Fitzinger wished to express thereby merely the amount of morphological resemblance, and there is no evidence whatever in the text that he had a clear idea of genetic affinity. The Batrachians are placed at the bottom of the scheme, leading through Hyla to the Geckos (clearly on account of the digital dilatations) and through Caeci! a to Amphisbaena. At the top Draco leads through Pterodactylus to the Bats (Pteropus), Ichthyosaurus to the Cetaceans (Delphinus), Emys to the Monotremes, Testudo to Manis, and the Marine Turtles to the Divers and Penguins. In Fitzinger's system the higher groups are, in fact, identical with those proposed by Merrem, while greater originality is shown in the subdivision of the orders. He differed also widely from Wagler in his views as to the relations of the extinct forms. The order of Loricata consists of two families, the Ichthyosauroidea and Crocodiloidea, the former comprising Iguanodon, Plesiosaurus, Saurocephalus and Ichthyosaurus. In the order Squamata Lacertilians and Ophidians are combined and divided into twenty-two families, almost all based on the most conspicuous external characters: the first two, viz. the Geckos and Chameleons, are natural enough, but in the three following Iguanoids and Agamoids are sadly mixed, Pterodactyles and Draco forming one family; Megalosaurus, Mosasaurus, Varanus, Tejus, &c., are associated in another named Ameivoidea; the Amphisbaenidae are correctly defined; the Colubroidea are a heterogeneous assemblage of thirty genera; but with his family of Bungaroidea Fitzinger makes an attempt to separate at least a part of the venomous Colubrine Snakes from the Viperines, which again are differentiated from the last family, that of Crotaloidea. If this little work had been his only performance in the field of herpetology his name would have been honourably mentioned among his fellow-workers. But the promise of his early labours was not justified by his later work, and if we take notice of the latter here it is only because his name has become attached to many a reptile through the pedantic rules of zoological nomenclature. The labours of Wiegmann, Müller, Duméril and Bibron exercised no influence on him, and when he commenced to publish a new system of reptiles in 1843, of which fortunately one fasciculus only appeared, he exhibited a classification in which morphological facts are entirely superseded by fanciful ideas of the vaguest kind of physiosophy, each class of vertebrates being divided Neue Classification der Reptilien nach ihren natürlichen Verwandtschaften (Vienna, 1826, 4to). 6 Systema Reptilium (Vienna, 1843, 8vo). into five "sense series, and each series into three orders, one comprising forms of superior, the second of medium and the third of inferior development. In the generic arrangement of the species, to which Fitzinger devoted himself especially in this work, he equally failed to advance science. We have now arrived at a period distinguished by the appearance of a work which superseded all its predecessors, which formed the basis for the labours of many succeeding years, and which will always remain one of the classical monuments of descriptive zoology-the Erpétologie générale ou histoire Duméril naturelle complète des reptiles of A. M. C. DUMÉRIL and and G. BIBRON (Paris, 8vo). The first volume appeared in Bibron. 1834, and the ninth and last in 1854. No naturalist of that time could have been better qualified for the tremendous undertaking than C. Duméril, who almost from the first year of half a century's connexion with the then largest collection of Reptilia had chiefly devoted himself to their study. The task would have been too great for the energy of a single man ; it was, therefore, fortunate for Duméril that he found a most devoted fellow-labourer in one of his assistants, G. Bibron, whose abilities equalled those of the master, but who, to the great loss of science, died (in 1848) before the completion of the work. Duméril had the full benefit of Bibron's knowledge for the volumes containing the Snakes, but the last volume, which treats of the Tailed Batrachians, had to be prepared by Duméril alone. The work is the first which gives a comprehensive scientific account of reptiles generally, their structure, physiology and literature, and again each of the four orders admitted by the authors is introduced by a similar general account. In the body of the work 121 Chelonians, 468 Saurians, 586 Ophidians and 218 Batrachians are described in detail and with the greatest precision. Singularly enough, the authors revert to Brongniart's arrangement, in which the Batrachians are co-ordinate with the other three orders of reptiles. This must appear all the more strange as Von Baer1 in 1828, and J. Müller2 in 1831, had urged, besides other essential differences, the important fact that no Batrachian embryo possesses either an amnion or an allantois, like a reptile. 4. Period of the Separation of Reptiles and Batrachians as Distinct Classes or Subclasses. In the chronological order which we have adopted for these historical notes, we had to refer in their proper places to two herpetologists, Blainville and Latreille, who advocated a deeper than merely ordinal separation of Reptiles from Batrachians, and who were followed by J. Müller F. S. Leuckart. But this view only now began to find and more general acceptance. J. MULLER and STANNIUS Stannlus. were guided in their classification entirely by anatomical characters, and consequently recognized the wide gap which separates the Batrachians from the Reptiles; yet they considered them merely as subclasses of the class Amphibia. The former directed his attention particularly to those forms which seemed to occupy an intermediate position between Lacertilians and Ophidians, and definitely relegated Anguis, Pseudopus, Acontias to the former, and Typhlops, Rhinophis, Tortrix, but also the Amphisbaenoids to the latter. Stannius interpreted the characteristics of the Amphisbaenoids differently, as will be seen from the following abstract of his classification : SUBCLASSIS: AMPHIBIA MONOPNOA (Leuckart). SECT. I. STREPTOSTYLICA (Stann.). Quadrate bone articulated to the skull; copulatory organs paired, placed outside the cloacal cavity. ORDO I. OPHIDIA. Subordo I. EURYSTOMATA or MACROSTOMATA (Müll.). The facial bones are loosely connected to admit of great extension of the wide mouth. Subordo 2. ANGIOSTOMATA or MICROSTOMATA (Müll.). Mouth narrow, not extensile; quadrate bone attached to the skull and not to a mastoid. 1 Entwicklungsgeschichte der Thiere, p. 262. 2 Tiedemann's Zeitschrift für Physiologie, vol. iv. p. 200. 3 Siebold and Stannius, Handbuch der Zootomie-Zootomie der Amphibien (2nd ed., Berlin, 1856, 8vo). This classification received the addition of a fifth Reptilian order which with many Lacertilian characters combined important Crocodilian affinities, and in certain other respects differed from both, viz. the New Zealand Hatteria, which by its first describers had been placed to the Agamoid Lizards. A. GÜNTHER, who pointed out the characteristics of this reptile, considered it to be co-ordinate with the other four orders of reptiles, and characterizes it thus :— Rhynchocephalia. Quadrate bone suturally and immovably united with the skull and pterygoid; columella present. Rami of the mandible united as in Lacertilians. Temporal region with two horizontal bars. Vertebrae amphicoelian. Copulatory organs, none. 5. Period of the Recognition of a Class of Reptilia as Part of the Sauropsida. Although so far the discovery of every new morphological and developmental fact had prepared naturalists for a class separation of Reptiles and Batrachians, it was left to T. H. Huxley to demonstrate, not merely that the weight of facts demanded such a class separation, but that the reptiles hold the same relation to birds as the fishes to Batrachians. In his Hunterian Lectures (1863) he divided the vertebrates into Mammals, Sauroids and Ichthyoids, subsequently substituting for the last two the terms Sauropsida and Ichthyopsida. The Sauropsida contain the two classes of birds and reptiles, the Ichthyopsida those of Batrachians and fishes. 6. Period of the Consideration of Skeletons of Extinct Reptiles.SIR R. OWEN, while fully appreciating the value of the osteological characters on which Huxley based his division, yet Owen. admitted into his consideration those taken from the organs of circulation and respiration, and reverted to Latreille's division of warm- and cold-blooded (haematothermal and haematocryal) vertebrates, thus approximating the Batrachians to reptiles, and separating them from birds. The reptiles (or Monopnoa, Leuck.) thus form the highest of the five subclasses into which, after several previous classifications, Owen finally divided the Haematocrya. His division of this subclass, however, into nine orders, makes a considerable step in the progress of herpetology, since it takes into consideration for the first time the many extinct groups whose skeletons are found fossil. He shows that the number of living reptilian types bears but a small proportion to that of extinct forms, and therefore that a systematic arrangement of the entire class must be based chiefly upon osteological characters. His nine orders are the following: a. ICHTHYOPTERYGIA (extinct)-Ichthyosaurus. b. SAUROPTERYGIA (extinct)-Plesiosaurus, Pliosaurus, Notho saurus, Placodus. C. ANOMODONTIA odon. d. CHELONIA. (extinct)-Dicynodon, Rhynchosaurus, Ouden e. LACERTILIA (with the extinct Mosasaurus). f. OPHIDIA. g. CROCODILIA (with the extinct Teleosaurus and Streptospondylus). h. DINOSAURIA (extinct)—Iguanodon, Scelidosaurus and Megalo saurus. i. PTEROSAURIA (extinct)-Dimorphodon, Rhamphorhynchus and Pterodactylus. Owen was followed by Huxley and E. D. Cope, who, however, restricted still more the selection of classificatory characters by relying for the purposes of arrangement on a few parts of the "Contribution to the Anatomy of Hatteria (Rhynchocephalus, Owen)," in Phil. Trans. (1867), part ii. 5 An Introduction to the Classification of Animals (London, 1869, 8vo), pp. 104 seq. Anatomy of Vertebrates (London, 1866, 8vo), vol. i. p. 6.” 7 Op. cit. p. 16. skeleton only. They attempted a further grouping of the orders which in Owen's system were merely serially enumerated as cosubordinate groups. HUXLEY used for this purpose Huxley. almost exclusively the position and character of the rib-articulations to the vertebral centra, the orders themselves being the same as in Owen's system : A. PLEUROSPONDYLIA. verse processes and not movable upon one another, nor are the ribs movable upon the vertebrae. A plastron. Order I, CHELONIA. Dorsal vertebrae devoid of trans B. The dorsal vertebrae (which have either complete or rudimentary transverse processes) are movable upon one another, and the ribs upon them. No plastron. a. The dorsal vertebrae have transverse processes which are either entire or very imperfectly divided into terminal facets (ERPETOSPONDYLIA). a. Transverse processes long; limbs well developed, paddles; sternum and sternal ribs absent or rudiment ary. Order 2, PLESIOSAURIA (=Sauropterygia, Ow.). B. Transverse processes short. aa. A pectoral arch and urinary bladder. Order 3, bb. No pectoral arch and no urinary bladder. Order b. The dorsal vertebrae have double tubercles in place of transverse processes (PEROSPONDYLIA). Limbs paddle-shaped. Order 5, ICHTHYOSAURIA (=Ichthyopterygia, Ow.). c. The anterior dorsal vertebrae have elongated and divided transverse processes, the tubercular being longer than the capitular division (SUCHOSPONDYLIA). a. Only two vertebrae in the sacrum. Order 6, CROCO DILIA. B. More than two vertebrae in the sacrum. aa. Manus without a prolonged ulnar digit. aa. Hind limb Saurian. Order 7, DICYNODON- BB. Hind limb Ornithic. Order 8, ORNITHO- bb. Manus with an extremely long ulnar digit. Order COPE, by combining the modifications of the quadrate and supporting bones with the characters used by Huxley, further developed Owen's classification, separating the Cope, Pythonomorpha and Rhynchocephalia as distinct orders from the Lacertilia. He eventually 2 elaborated the following classification, based entirely on osteological characters :-- I. The quadrate bone immovably fixed to the adjacent elements by suture. A. Scapular arch external to ribs; temporal region with a complex bony roof; no longitudinal postorbital bars. A tabular and supramastoid bones and a presternum ; limbs ambulatory; vertebrae amphicoelous. Order 1, COTYLOSAURIA. AA. Scapular arch internal to ribs; temporal region with complex roof and no longitudinal bars. A presternum; limbs ambulatory. Order 2, CHELYDO SAURIA. AAA. Scapular arch internal to ribs; sternum extending below coracoids and pelvis ; one post orbital bar. No supramastoid; a paroccipital; clavicle not articulating with scapula. Order 3, TESTUDINATA. AAAA. Scapular arch external to ribs; one longitudinal postorbital bar (Synaptosauria). A supramastoid and paroccipital bones; ribs two-headed A supramastoid; paroccipital not distinct; a post orbito- AAAAA. Scapular arch external to ribs; two longitudinal post- Ribs two-headed; a clavicle and interclavicle; aceta- 1 Proc. Amer. Assoc. for the Advancement of Science, 10th meeting (Cambridge, 1871, 8vo), pp. 230 sq.; Amer. Naturalist (1889), vol. xxiii. p. 863. 1. Syllabus of Lectures on the Vertebrata (Philadelphia, 1898, 8vo), P. 54. Ribs two-headed; interclavicle not distinct; external digits greatly elongated to support a patagium for flight. Order 8, ORNITHOSAURIA. Ribs two-headed; no interclavicle; acetabulum open; ambulatory. Order 9, DINOSAURIA. Ribs two-headed; an interclavicle; acetabulum closed; ambulatory. Order 10, LORICATA. Ribs one-headed; an interclavicle; acetabulum closed, a large obturator foramen; ambulatory. Order 11, RHYNCHOCEPHALIA. II. The quadrate bone loosely articulated to the cranium and at the proximal end only (Streptostylica). No distinct supramastoid, nor opisthotic; one or no postorbital bar; scapular arch, when present, external to ribs; ribs one-headed. Order 12, SQUAMATA. While this classification was being considered and prepared, both Cope and G. Baur made a special study of the bones which surround the quadrate and arch over the biting muscles in the various groups of reptiles. This led to a series of discussions which ended in the idea, that the class could be most naturally divided into two great subclasses, the one culminating in tortoises and mammals, the other in crocodiles, lizards, snakes and birds. Professor H. F. OSBORN in 1903 3 therefore proposed the following classification :— Subclass SYNAPSIDA. Primarily with single or undivided temporal arches. Giving rise to the mammals through some unknown member of the Anomodontia. Osborn. Orders Cotylosauria, Anomodontia, Testudinata and Sauropterygia. Subclass DIAPSIDA. Primarily with double or divided temporal arches. Giving rise to the birds through some unknown type transitional between Protorosauria and Dinosauria. Orders Diaptosauria (= Protorosauria, Pelycosauria and Rhynchocephalia), Phytosauria (= Belodon, &c.), Ichthyosauria, Crocodilia, Dinosauria, Squamata and Pterosauria. The most exhaustive and modern general work on reptiles is by Dr C. K. HOFFMANN in Bronn's Klassen und Ordnungen des Thierreichs (1879–90). A most useful and less technical treatise is the volume on Amphibia and Reptiles contributed by Dr H. Gadow to the Cambridge Natural History (London, 1902). Hoffmann. (A. C. G.; A. S. Wo.) II. GENERAL CHARACTERS OF THE CLASS REPTILIA Reptiles, as known in the existing world, are the modified, and in many respects degenerate, representatives of a group of lung-breathing vertebrate animals which attained its maximum development in the Mesozoic period. So far as can be judged from the skeleton, some of the members of this group then living might have become mammals by very slight change, while others might as readily have evolved into birds. It is therefore probable that the class Reptilia, as now understood, comprises the direct ancestors both of the Mammalia and Aves. Assuming that its extinct members, which are known only by skeletons, were organized essentially like its existing representatives, the class ranks higher than that of the lowest five-toed vertebrates (class Batrachia) in the investment of the foetus by two membranous envelopes (the amnion and allantois), and in the total absence of gills even in the earliest embryos. It ranks below both the Mammalia and Aves in the partial mixture of the arterial blood with the venous blood as it leaves the heart, thus causing the organism to be cold-blooded; it also differs both from Mammalia and Aves in retaining a pair of aortic arches, of which only the left remains in the former, while the right one is retained in the latter. No feature in the endoskeleton is absolutely distinctive, except possibly the degeneration of the parasphenoid bone, which separates the Reptilia from the Amphibia. In the exoskeleton, however, the epidermis forms horny scales, such as never occur in Amphibia, while there are no traces of any structures resembling either hairs or feathers, which respectively characterize Mammalia and Aves. There is little doubt that true reptiles date back to the latter part of the Palaeozoic period, but at that epoch the Amphibia approached them so closely in the characters of the skeleton that it is difficult to distinguish the members of the two classes among the fossils. Some of the Palaeozoic Amphibia-a few of the so-called Labyrinthodonts-are proved to have had welldeveloped gill-arches in their immature state, while there are conspicuous marks of slime-canals on their skulls. Others are 3 Mem. American Mus. Nat. Hist. (November 1903), vol. i. art. viii. of the upper, bar, some members of this series eventually pass into the order Squamata (Lacertilia +Ophidia), in which the quadrate bone is completely exposed and loosely attached to the skull (fig. 2, E); other reptiles exhibiting a similar modification may readily have acquired the typical Avian skull | (fig. 2, F) by the loss of the upper and the retention of the lower temporal bar in question. FIG. 1.-A, Palate of Palaeozoic Amphibian (Archegosaurus decheni). B, Palate of Mesozoic Reptile (Plesiosaurus macrocephalus). b.occ, basioccipital; bs, basisphenoid; eept, ectopterygoid; i.pt, interpterygoid vacuity; j, jugal; mx, maxilla; pas, parasphenoid; pl, palatine; pmx, premaxilla; pt, pterygoid; pt. nar, posterior nares; qu, quadrate; s.o, suborbital vacuity; v, vomer. which less resemble the typical Labyrinthodonts are characterized by the reduction of the parasphenoid bone so that it no longer reaches the vomers; in these animals the weakened skull exhibits a secondary basicranial axis formed by the approximation of the pterygoids to the median line (fig. 1, B). The latter condition is universal in existing reptiles, and may therefore perhaps be regarded as a diagnostic feature. If so, the oldest known undoubted reptile is Palaeohatteria, from the Lower Permian of Saxony. In the structure of the skull Palaeohatteria is much like the existing Sphenodon, the cheek-plates which cover the temporal and masseter muscles on each side being pierced by two great vacuities, one superior-temporal, the other lateral-temporal. The majority of the earliest reptiles, however, either resemble the Labyrinthodonts in having the biting muscles completely covered with a roof of bony plates, or exhibit a slight shrinkage of this investment so that a superior-temporal vacuity appears. As the various groups or orders become differentiated, this shrinkage or reduction continues, while the shape of the ossifying ear-capsule changes, and the squamosal bone, which covers the organ of hearing in the fishes, and presumably also in the Palaeozoic Batrachia, is gradually thrust outwards from all connexion with this capsule except at its hinder angle. The resultant modifications are diagrammatically represented in fig. 2. In one series of orders, comprising the Anomodontia, Chelonia, Sauropterygia and Ichthyopterygia (fig. 2, B, C), the superior-temporal vacuity (s) first appears; and the cheekplates in the broad temporal arch thus formed may be variously fused together, sometimes even irregularly perforated-showing at first, indeed, the usual inconstancy of a new and not completely established feature. From the earliest members of this series of reptiles, palaeontology seems to demonstrate that the Mammalia (with one robust temporal arcade or zygomatic arch) arose. In a second series, comprising the orders Rhynchocephalia, Dinosauria, Crocodilia and Ornithosauria (fig. 2, D), the broad arch of cheek-plates is regularly pierced by a lateraltemporal vacuity, which leaves a narrow bar above, another narrow bar below, and uncovers the middle part of the quadrate bone. By the constant loss of the lower, and the frequent loss In view of these and other palaeontological considerations, the Reptilia may be classified into orders as follows: 2. Chelonia.—Postero-lateral region of skull as in Anomodontia, except bones of ear-capsule more modified. No pineal foramen. Ribs single-headed. No sternum. Pectoral and pelvic arches unique in being situated completely inside the ribs. No epicoracoid. Abdominal ribs replaced by three or four pairs of large plates, which, with the clavicles and interclavicle, form a plastron. Limbs only for progression; third and fourth digits with not more than three phalanges. A regular dorsal carapace of bony plates intimately connected with the neural spines, and ribs of seven to nine dorsal vertebrae. Range.-Upper Triassic to Recent. 3. Sauropterygia. - Bones of postero-lateral region of skull contracted into a single broad zygomatic arch, leaving a superior-temporal vacuity. Pineal foramen present. No fused sacral vertebrae. All dorsal ribs single-headed, articulating with transverse processes of the neural arches. Abdominal ribs forming dense plastron. Apparently no sternum. Coracoid, pubis and ischium in form of much-expanded plates. Limbs modified as paddles, with not more than five digits, of which the third and fourth always have more than three phalanges; all digits usually consisting of numerous phalanges. No dermal armour. Range.-Upper Triassic to Cretaceous. 4. Ichthyopterygia.-Bones of postero-lateral region of skull contracted into a single broad zygomatic arch, leaving a superiortemporal vacuity. Pineal foramen present. Vertebral centra short and deeply biconcave, with feeble neural arches which are almost or completely destitute of zygapophyses. No fused sacral vertebrae. Cervical and dorsal ribs double-headed, articulating with tubercles on the vertebral centra. Abdominal ribs forming dense plastron. Apparently no sternum. Coracoid an expanded plate, probably with cartilaginous epicoracoid. Pelvis very small, not connected with vertebrae. Limbs with vertebrae. Limbs modified as paddles, with digits of very numerous short phalanges, which are closely pressed together, No dermal sometimes with supplementary rows of similar ossicles. armour. A vertical triangular caudal fin, not supported by skeletal rays. Range. Triassic to Cretaceous. 5. Rhynchocephalia.-Bones of postero-lateral region of skull contracted into two slender zygomatic bars, leaving a superiortemporal and a lateral-temporal vacuity, and partly exposing the quadrate bone from the side. Pineal foramen present or absent. Ribs single-headed. Abdominal ribs present. Sternum present. Epicoracoid cartilaginous. Limbs only for progression; third and fourth digits with four or five phalanges. Dermal armour feeble or absent. Range.-Lower Permian to Recent. 6. Dinosauria.-Postero-lateral region of skull as in Rhynchoheaded. Rarely abdominal ribs. Sternum present, but apparently cephalia. No pineal foramen. Cervical and dorsal ribs doubleno clavicular arch. Limbs for support as well as progression; third and fourth digits with four and five phalanges respectively. Dermal armour variable. Range. Triassic to Cretaceous. 7. Crocodilia.-Postero-lateral region of skull as in Rhynchocephalia. No pineal foramen. Cervical and dorsal ribs doubleheaded. Abdominal ribs present. Sternum present; also interclavicle, but no clavicles. Limbs only for progression on land or swimming; third and fourth digits with four or five phalanges. Dermal armour variable. Range.-Lower Jurassic to Recent. 8. Ornithosauria.-All bones extremely dense, light and hollow, the organism being adapted for flight. Postero-lateral region of skull as in Rhynchocephalia. No pineal foramen. Cervical and dorsal ribs double-headed. Abdominal ribs present. Sternum present, and keeled for attachment of pectoral muscles; no clavicular arch. Fifth digit of hand much elongated to support a wingmembrane, but with only four phalanges. Hind limb feeble. No dermal armour. Range.-Lower Jurassic to Cretaceous. |