64 REPORT — 1841. 



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prominent. The non-articular surface of the centrum is not very regular, but 

 is smooth ; the lower surface is square-shaped, and nearly flat ; its angles are 

 marked by the haemapophysial surfaces, of which the anterior pair is the 

 largest. 



Bones of the Extremities. — The type of construction of the bones of the 

 extremities closely accords with that of the Plesiosaur. The pectoral arch 

 owes its chief strength to a pair of immensely expanded coracoids, having a 

 broad and short entosternal bone on their anterior interspace, and supporting 

 the clavicles, or the acromial productions of the scapulae. 



The femur of the Market-Raisin specimen measures two feet two inches in 

 length, and is thirteen inches broad at its distal end — a bone well fitted to 

 support and wield the strong paddle that must have been mainly instrumental 

 in propelling this carnivorous sea-monster through its native element. 



In another femur, measuring thirteen and a half inches across the distal 

 end, the circumference of the proximal end was nearly two feet ; the upper 

 half of the bone is cylindrical ; it gradually exclianges this for a compressed 

 expanded distal end, which is terminated by a pretty regular convex curve. 

 The texture of the bone is coarsely cellular throughout, being devoid, as in 

 other marine Saurians, of any trace of medullary cavity. 



One of the siibcircular carpal bones of the Market-Raisin specimen mea- 

 sured five and a half inches across the broadest part, and four and a half 

 across the narrowest, and was two and a half inches in thickness. 



The phalanges are short and less compressed than in the Plesiosaurs ; flat 

 at the articular extremities, and remarkably contracted in the middle. 



Besides the localities affording specimens from which the general descrip- 

 tion of the bones of the trunk and extremities is taken, and which localities 

 are noticed in that description, remains of the Pliosaur have been discovered 

 in the following localities : — A small cervical vertebra from Shotover, in 

 the Oxford Museum ; four dorsal vertebrae, equal in size with the Market- 

 Raisin specimen, from Marcham, also in the Oxford Museum ; the vertebra 

 in the Yorkshire Museum*, said to have been found in the gravel of Burn, one 

 mile below Nunnykirk, Northumberland, and noticed in the first edition of 

 Lyell's ' Principles of Geology,' is a posterior cervical of a Pliosaurus, and 

 must be presumed to have been accidentally introduced into that recent de- 

 posit. The several specimens from these different localities yield strong indi- 

 cations of two distinct species of the presept gigantic genus, which connects 

 the Enaliosaurs with the Coelospondylian Crocodiles. The difference in breadth 

 and height, and especially in the size of the hatchet-bone, or cervical rib, as 

 indicated by the articular surface, appear to be inexplicable, except on the 

 supposition of two distinct species. The difference is continued in the dorsal 

 vertebrae, the transverse processes of which are more compressed, and the non- 

 articular surface more rugous in the Shotover than in the Market-Raisin spe- 

 cies. The two forms of femora, on which the species Plesiosauri grandis 

 and trochanterius are founded in the former part of this Report, are both 

 referable to the genus Pliosaurus ; but have not as yet been found so asso- 

 ciated with vertebrae as to aid, in combination with the vertebral characters, 

 in the definition of the two species. When subsequent discoveries and ob- 

 servations shall have supplied distinct and recognizable characters to the two 

 species of the present very remarkable and interesting annectant genus, the 

 term hrachydeirus, which I had first proposed for the species represented by 



* In the Yorkshire Museum there is preserved a humerus of a Pliosaur from the lower part 

 of the Kimmeridge clay deposit at Speaton, which measures thirteen inches in length, and 

 seven inches across the distant end : the femur of the same specimen measured sixteen 

 inches in length. 



