LIASSIC FORMATIONS. 
19 
skeleton (Tab. V) is fourteen feet, which would be increased by several inches were 
the tail entire and outstretched. 
The specimen of PI. homalosj)ond)/lus in the Museum of the Yorkshire Philosophical 
Society is larger than the one in the British Museum, but has been lithographed on a 
smaller scale in Tab. VIII ; it measures 10 feet 6 inches in total length. It lies in a 
somewhat similar posture to that in the British Museum, but with the long and 
slender neck and anterior dorsals bent so as to give a concavity to the dorsal con- 
tour of the animal ; the caudal vertebrae, which are better preserved, are also bent in 
the same direction, and all the vertebrae follow in their consecutive undisturbed 
juxta-position in both skeletons. The numbers of the vertebrae in the cervical and 
dorsal series respectively appear to be the same. The diapophysis has got entire 
possession of the rib at the fortieth vertebra, counting from the head •, and the costal 
surface begins, with its process, to sink again upon the centrum, at the sixty-seventh 
vertebra, which the thickness of the diapophysis indicates to be a sacral vertebra. 
Beyond this may be counted twenty-seven caudal vertebrae, and it is not probable 
that their number exceeded thirty. 
The cervical vertebrae show the same distinctive characters of the species which 
have been already defined; the neural spine is preserved in a much greater proportion 
of the cervical series ; in the fifteenth cervical it shows a height of two inches, and a 
nearly equal antero-posterior breadth; with a broadly truncate summit, having the 
angles rounded off. The vertebrae keep their proportion of length from this point to 
the end of the dorsal series ; they then grow shorter to the end of the tail, tliroughout 
the greater part of which the centrum is deeper, and the neural spines longer and 
narrower, than in the neck, indicative of the greater mass of muscle operating on the 
tail, and also its greater flexibility in a given extent. The costal series has sulfered 
much more displacement and loss in the York specimen than that in the British 
Museum; the larger ribs are a good deal jumbled and broken in the region of the 
trunk or thoracic abdominal cavity, but they show the same massive character. The 
ischio-pubic part of the pelvis has been drawn away, at an acute angle, from the ilium 
and sacrum; its inner or upper surface is exposed at 63, 61, Tab. VIII. The right 
pelvic limb has been moved forward, with the head of the femur lying upon the lower 
end of the right coracoid. The right pectoral limb extends forward from near its 
normal place of articulation with the coracoid ; but it has been turned bodily over, 
showing its inner or palmar surface. The limbs of the left side are huddled in a dislo- 
cated and incomplete state beneath the hinder part of the trunk. 
The presence of both these limbs, in an excellent state of preservation, supplies the 
chief deficiency in the specimen in the British Museum previously described. 
The pectoral limb, as in PI. dolichodeirus, is rather shorter than the pelvic one ; 
its entire length is 3 feet 8 inches, equalling sixteen vertebrae towards the base of the 
neck. The humerus, 13 inches in length and 7^ inches in distal breadth, is broader 
