shade and moisture, numerous ferns, and even tree ferns are found, as in Silhet. The strata of the Burdwan coal-basins of Ranigunge and Chinakooree yielded the author abundant remains of the Ranigunge reed, Vertebraria indica, the marsileaceous genus, Trizygia speciosa, and species of Pecopteris, Glossopteris, &c. G. Browniana is interesting as having been found in these coal-fields, and according to Brongniart, in New Holland, in the coal of the Hawkesbury river, near Port Jackson. Zamia Buchanani has also been found, and a palm which has been called Zeugophyllites calamoites. With a little more moisture, or even the umbrageous covering of a forest, these, and other similar plants, would grow with luxuriance in these localities. Seeing therefore that heat, with moisture, is capable at the present day of supporting a vegetation similar to that of coal-fields, it would in ancient times only have required the presence of heat and moisture for the vegetation of coal-fields to have flourished. If the mass of the earth was in ancient times of a higher temperature, as is inferred from many geological and zoological phænomena, it is evident that, water being present, copious evaporation would necessarily take place as it now does in tropical countries. If the internal heat were uniform at different points of the globe's surface, then would the evaporation be uniform, and there would be an absence of those upper and lower currents of the atmosphere which now carry the heated and moisture-loaded air of the tropics to polar regions, and send the cold air of the latter towards the equator. As the air, loaded with moisture, ascended into the atmosphere, it would at length reach an elevation where the reduction of temperature would proceed beyond the point of deposition of moisture, and the whole of what had been raised by the aid of heat and air would be constantly depositing in the form of clouds and rain. Moisture would thus everywhere be preserved, and the cloudiness from the steady action of the heat below and of the cold above would necessarily also be constant. This would produce uniformity of temperature; for radiation from the surface would be obviated, and the solar rays would not penetrate the cloudy canopy more than they do in rainy weather at the present time. In such a climate, tropical plants would be able to grow equally well in any latitude, and there might be intermixed with them many others to which dryness was not essential. In conclusion, the author remarked, such a cloudy canopy may be observed to a partial extent, even in the present day. Humboldt has described it as occurring on the Andes; the author had himself observed it for days together on the Himalayas, and partially so during the whole of the rains; Dr. M'Clelland and others have described it as occurring for months together in the valley of Assam. If it existed in northern regions in early times, and the sources of heat were, as Dr. Royle assumed, internal, then could tropical vegetation not only exist in polar regions during the summer season, but it would not be destroyed in winter. Growth would only be stopped, as in the present day, during the darkness of night. As the internal heat diminished and receded from the surface, the cloudy canopy would by degrees be at a lower and a lower elevation, until, like the snow-line of the present, it would be at the surface of the earth in high latitudes. These regions would become as they are now, and immediately under the influence of external cold, and thus a glacial might succeed a tropical vegetation. In situations where a lofty peak raised itself above the canopy of clouds, it would become exposed to the cooling effects of radiation, and would, as in the present day, attract to itself and condense much of the floating moisture of the atmosphere, and give origin to mighty and rapid rivers, which would plough the mountain side and overspread the level plain.

A Synopsis of the Classification of the Genera of British Birds.
By JOHN HOGG, M.A., F.R.S., F.L.S., &c.

The author, having completed his classification of birds, which has been carried out on the same principles as that portion published in the Report of the Fourteenth Meeting of the British Association, although in some respects modified from it, gave in this communication his arrangement of the genera of the birds hitherto met with in the British Islands.

It will be seen that he has been compelled to increase the families, and that he has not inserted the subfamilies, esteeming them unnecessary, and as too much lengthening the classification. The author has been very careful in the choice of the

genera, and he trusts it will be found that he has only retained those which are really distinct; and whilst he has, after due consideration, thought it requisite to add to the number of those which British ornithologists usually employ, he has at the same time reduced those too numerous genera of certain authors, and especially of the Prince of Canino. Likewise, with regard to subgenera, the use of which the author must always maintain to be extremely disadvantageous to science, he has wholly omitted all notice of them.

*The author's Order II. Prehensores entirely consists of foreign birds, which belong to the Genus Psittacus of Linnæus. His proposed divisions of this order are given in Jameson's Edinburgh Phil. Journal for July, 1846.

List of the Names of Periodical Birds, and the dates of their appearance and disappearance, at Llanrwst, in North Wales. By JOHN BLACKWALL, F.L.S.

Mr. Gould exhibited several new species of humming-birds from the Andes.

On the Figures of Birds observed on a Tomb at Memphis. By J. BONOMI. Since his last communication the author had received the following note from Mr. Moreing:-"The gigantic nests to which you refer, were seen by me in the years 1829 and 1830, during the time I was attached to the Surveying Expedition in the Red Sea. I do not remember having seen them to the south of Cossier, but to the north of that town, and about the entrance to the Sea of Suez, I observed many. They were always situated on the small sandy spits and islands with which the Red Sea abounds; but you are mistaken if you suppose them to be entirely the work of the birds which breed in them. They varied both in size and height, and were evidently formed in the first instance by the wash of the sea heaving up pieces of broken coral, drift wood, and other rubbish on the extremity of a sand spit. The birds added to the mound thus formed; and placed their nests on the top, to protect themselves from the spray in rough weather. I am not clear as to the species of bird which make use of these singular nests, but believe that more than one kind of gull avail themselves of the security thus offered."

On the Crania of two species of Crocodile from Sierra Leone.
By H. FALCONER, M.D. and W. THOMPSON*.

Crocodilus cataphractus, Cuv. and C. vulgaris, Cuv. (var. C. Dumeril and Bibron), were the species noticed; the cranium of the former, divested of its integuments, being now for the first time described. The differences between the cranium of the latter and that of allied species were noticed in detail in the paper, which was illustrated by figures of the crania of the two forms from Sierra Leone, whence the specimens were brought by Dr. M'Cormac of Belfast, and presented by him to the museum of that town.

Recollections of Researches into the Natural and Economie History of certain Species of the Clupeada, Coregoni, and Salmonida. By R.KNOx, M.D.

The author stated that his object was to bring before the Association, and afterwards before the Academy of Sciences of Paris, a brief view of the inquiries made by himself and his brother into the natural history of certain important gregarious fishes. His discovery that the food of the Vendace or Vengis, of Lochmaben, cousisted exclusively of the minute, or rather microscopic Entomostraca inhabiting the lakes of Lochmaben, was first communicated to the Royal Society of Edinburgh, This discovery, which at the time appeared to the author and to a few others of the highest importance in natural history science, had, in his opinion, been misunderstood by the public, and by most naturalists to whom he had spoken; they adhering to the old opinion, that certain fishes, to be afterwards spoken of, preyed on the Entomostraca merely occasionally; at other times on small shell-fish, animalcules, minute or small fishes, &c., just as they could get them; which opinions the author endeavoured to show were contrary to the facts. After discovering that fishes so numerous, so productive and of such a size as the Vendace, subsisted solely on one description of food, the Entomostraca,—a sort of food over which man can exercise little control, especially in the ocean, the author knowing that, up to his time, the real food of the herring and of several other species of fish had never heen discovered, prosecuted his inquiries into this important branch. The result was the discovery that, whilst the Vendace lives exclusively on the Entomostraca, the same may be said of the herring; that is, of most of its varieties. The finer kinds of lake trout, also the Char, live chiefly on the Entomostraca. Dr.Knox gave an outline of * Published in full, accompanied by illustrations, in the Annals of Nat. Hist. for Dec. 1846.

a superior kind of trout, which he thinks has not been described by naturalists: he calls it the "Estuary Trout," brackish waters being the locality it prefers. Its food differs from all others he has examined. Should it prove, on future inquiry, that the brackish water is the limit to its usual, or natural range, it may furnish a means of deciding on some difficult legal questions. As regards the celebrated questions raised by the Drumlanrig experiments, to which his first memoir gave, as he believes, the exciting cause, Dr. Knox thinks it not proved that the salmon smolt, that is the young salmon, ever remains longer in the river than a few weeks after rising from the gravel; and thinks that the opinions founded on the Drumlanrig experiments are in this respect erroneous. 2nd. As regards the question of the parr, no new fact was added to its previous history by these experiments; the parr markings, which may be again made visible on scraping off the scales of the smolt, was a fact well-known to anglers; who at the close of the day found it difficult to say which were true parr and which salmon smolts. Mr. Scrope first gave a beautiful drawing of this fact. 3d. For at least a hundred years the opinion that the parr was the young of the salmon prevailed universally in Annandale. 4th. Willoughby had proved that the salmon-egg may be impregnated by the milt of the parr; an experiment curious enough physiologically, but otherwise of no practical importance. 5th. Mr. Hogg and a great many others had marked the spring parr, and found that they returned to the rivers full-grown salmon. Thus no new fact was added to the natural history of the salmon by the Drumlanrig experiments. The author declined giving a decided opinion as to the real nature of the true parr; but, so far as his observations had yet gone, he believes that there is a fish which may be called the true parr, hitherto confounded with many other species having parr markings; and that this true parr may ultimately prove a hybrid between the salmon or salmon trout and certain species of river trout.

On the Application of the Method, discovered by the late Dr. Thibert, of Modelling and Colouring after Nature all kinds of Fishes. By R. Knox, M.D. These models were shown. They consisted of the Vendace, the mackerel, the red-spotted trout of England, and the Lochmaben trout. This method of modelling will ultimately be preferred to all others; even to that in wax.

On the Egg-purse and Embryo of a Species of Myliobatus.
By J. COUCH, F.L.S.

The author commenced by stating that the egg-purse was found in August 1845, in the refuse of a trawl-boat by Mr. Peach; and was obtained a few miles south of Fowey, in Cornwall. After mentioning how little is known of the egg-cases of the rays and sharks, he minutely described it; and showed the difference between it and others, particularly dwelling on the structure of the surface, it being reticulated, whereas all the other egg purses are smooth. In the egg-purse was a living young fish, which proves to belong to the genus Myliobatus of Cuvier, characterized by having the pectoral expansion separated from the head. These, from the direction of the wings, have been fancifully called sea-eagles. Ruysch, whose figures are for the most part copies from preceding authors without being improvements on the originals, but who, at plate 9. fig. 9, has given one tolerably characteristic, remarks that it has been called "Sea Toad," from the form of the head resembling that creature; and the comparison seems appropriate, from the elevated head with a protuberant and lateral eye. The same author says that this fish is viviparous; an assertion which the foregoing account shows to be incorrect.

On the Crustacea found by Prof. E. Forbes and Mr. McAndrew in their Cruises round the coast. By Prof. THOMAS BELL, F.R.S., F.L.S. &c. Having been requested by my friends Prof. Forbes and Mr. M'Andrew to communicate to the Section some observations on the contributions to carcinology made by those gentlemen in their recent cruises, I gladly comply with their wish; and although I have not to record many actual novelties in the species collected, yet