LIAS FORMATION. 
137 
this subject. The Museum of the Whitby Philosophical Society contains some of 
the most valuable of these remains, particularly a small but perfect ichthyosaurus, 
containing one hundred and thirty-six vertebrae, and a superb crocodile fifteen feet long. 
PI. XII. fig. 1, represents the basal surface of a small cranium of a crocodile, to shew 
the arrangement of the posterior bones, and fig. 2 is a copy of a singular head which 
seems to differ from any hitherto described ichthyosaurus. A drawing of the full size 
was given to Baron Cuvier. Both specimens are in the Museum of the Yorkshire 
Philosophical Society. 
The three divisions of the lias formation which have been described 
on the coast of Yorkshire, may be traced southward through Lincoln- 
shire, Rutland, Northamptonshire, Oxfordshire, Gloucestershire, and 
Somersetshire. Sections obtained in any part of this long range agree 
in representing the lias clay, as divided into two portions by an inter- 
mediate series of sandy and irony layers of stone, full of many organic 
remains. The upper division varies in thickness, and changes much in 
aspect and composition. Its thickness in Yorkshire sometimes equals 
two hundred feet, and in Rutland exceeds one hundred feet ; but in the 
neighbourhood of Bath may be stated at twenty feet. The marlstone 
series maintains a general conformity of character, and, though nowhere 
so thick or so much developed as in Yorkshire, constitutes an important 
feature in the range of the formation, especially in Rutland. The solid 
beds of gryphitic limestone which lie toward the base of the lias clay, 
from Somersetshire to Lincolnshire, may, with attention, be traced in the 
southern part of Yorkshire, but they nowhere appear on the coast. Mr. 
Murchison’s observations in the district of Brora, and at various points 
on the western coasts of Scotland, are decisive as to the occurrence of 
the lias there ; but I am unable to determine what particular divisions 
of the formation are exposed in the several localities. With great 
deference I beg to suggest that the section of the north-east coast of 
Skye, (Geological Transactions, New Series, VoL II. page 360,) would 
better coincide than it seems to do at present, with the series of 
the Yorkshire coast, if the following designations should prove correct : 
No. 1, upper sandstone and shale, (coaly grit of Smith.) 2. Cave oolite 
T 
