EXPLANATION OF PLATE XIV.

The great bulk of the intestines is raised towards the chest, bringing

into sight

L-Part of the under surface of the Liver.

K-The Kidneys.

U-The Ureters.

B-The Bladder.

R-The Rectum.

XXVI.

Geological Description of Anglesea.

By J. S. HENSLOW, M.A.; F.L.S.; M.G.S.

To accompany the present Memoir, I have formed a collection of the rocks of Anglesea, which has been placed in the Woodwardian Museum. This collection is numbered throughout, and the number corresponding to any particular specimen is, noted between brackets, whenever any allusion is made either to its locality or to the nature of its composition.

I have to acknowledge my obligations to L. P. Underwood Esq., whose previous visits to Anglesea had enabled him to collect many interesting facts connected with its Geology, and to whom I am indebted for the locality of several trap-dykes, which might otherwise have escaped my observation..

I believe that no good map of Anglesea has yet appeared. The map which accompanies this paper is compiled from two maps of North Wales, one by Furnival, published in 1814, the other by Evans, in 1797. The first of these furnishes, with condesirable correctness, the relative positions of the towns and general outline of the country, but does not pretend to trace the indentations of the coast. Evans has enabled me to give some

of the latter, where they affect the geological details; but neither in this respect, nor in the configuration of the surface, could I procure any accurate information. What is here offered must be considered as a very rough approximation.

As the map is rather complicated, it has been thought advisable to adopt an artificial arrangement of the different districts in each formation. By this means a reference can more readily be made to any particular place, without the labour of searching through the several detached portions marked by the same colour. A table explaining this arrangement is placed with the description of the plates; and the references are made on the margin whenever they seem to be required. No other places are noted in the map than those alluded to in the paper.

In the accompanying sections, continuous lines are meant to represent the portions actually exhibited. The dotted lines are either such portions as were not visited, or were too much obscured by the concealed nature of the ground. Where no actual section exists, the junctions are marked by the dotted line, even where the boundary between two formations is sufficiently evident at the surface, and the order of collocation has been either ascertained along the coast, or cannot be doubtful from the characters of the contiguous rocks. As the sections are parallel to each other, a reference may readily be made to corresponding portions, and the spot seen where the order was clearly established.

Anglesea possesses no no very striking features. Holyhead mountain, which forms the greatest elevation, reaches only to 709 feet above the sea. With this and two or three other exceptions, the ground is low and undulating, although the surface possesses by no means an uniform character. A further description may perhaps, with greater propriety, be referred to the details of each particular formation.

The plan of this paper will be, first to describe the stratified and then the unstratified rocks.

The greater portion of the stratified rocks has suffered considerable disturbance, and they frequently occur under characters very different from what they assume in their undisturbed state. Several of the details therefore, which would otherwise be included in this division, are deferred to the description of the unstratified masses; when it is to their intrusion that such phenomena can be referred..

Quartz Rock.

{Nos. 1. to 11.}

The term, Micaceous schist, would perhaps by some Geologists, be made to include the whole series of the oldest stratified rocks. These, however, vary considerably in composition, but do not allow of separation into distinct formations, and would scarcely admit of geographical distribution, even in a map of the largest dimensions and most accurate construction.

In one instance an exception may be made in favour of a variety, marked on the map as a quartz rock, which possesses certain peculiarities of structure, though it is not very remote in composition from other varieties included under the general denomination. It occupies two distinct localities, the one in the Q.1. northern division of Holyhead Island, lying to the West of a line drawn from Port-Dafreth, to a point on the shore about midway between Holyhead and the mountain. The other, in the Southern Q.2. division of that Island, occurs in the neighbourhood of Rhoscolyn, extending along the coast, and bounded by a line drawn from Borth-Wen to Rhoscolyn church, and thence about one mile further to the N.W. In each case this rock rises to a greater