344 Transactions.—Geology. 
in specimen 3 e, the length of the centrum is 2 inches, while the transverse and 
vertical diameter are З inches and 2:3 inches respectively. In specimen 3d a 
posterior dorsal vertebra, without the neural spine, is recognized as belonging 
to this species, by the transversely elongated tubercle and the character of the 
articular facet. One end of the centrum has been broken off, so that its 
length cannot be ascertained, but it measures transversely 4 inches, and 
vertically 3:3 inches. The lateral processes spring from the side of the 
centrum, and not from the inferior third, as in the cervical vertebre ; and 
the neuralspine, though broken off, has been distinctly continuous without 
any suture. This fusion of the neural arch, both in the anterior and posterior 
parts of the column thus indicated, confirms the suspicion that this species 
should be placed in a genus distinct from Plesiosawrus. On the same slab 
with this vertebra are thirty-two phalanges, exposed in their natural position 
in continuous rows ; the largest about 2'7 inches in length, cylindrical, and 
only moderately constricted at the middle. 
4. PLESIOSAURUS HOLMESII, n. sp. 
This species is allied to P. hoodii, in the trigonal form of the vertebral 
centrum and the strong wedge-shaped neural spine continuous with the body 
of the vertebre. They are, however, at once distinguished by their flat, 
smooth, articular surfaces, and the absence of the elongated tubercle in the 
centre. Eleven posterior cervical vertebrz (4 а) have a length in sitd of 2 feet. 
They were found on the exposed surface of a slab, and are therefore water- 
worn, so that their transverse dimensions obtained are not trustworthy, but they 
appear to have been about 3 inches in diameter. In the same slab is a fragment 
of a shaft of a humerus, and the margin of a coracoid (4 6, c), with a scapulo- 
humeral articulation, which seems to have resembled closely that of Mauisaurus. 
The proximal end of a humerus (4 d), found by Mr. McKay at the Amuri Bluff, 
has been referred to this species on account of associated vertebral fragments. 
The articular head of the bone is peculiar, being divided into two portions by 
`a bicipital notch, not a groove, as in Mawisawrus. The external part of the 
facet is a square, flat-topped, trochanter-like process, but continuous with the 
curve of the inner portion, which is nearly circular, convex, and deeply pitted, 
in the manner of Plesiosaurus. It is not improbable that both this and the 
last-mentioned species should be referred to Professor Owen’s genus of 
Pleiosaurus. 
5. PLESIOSAURUS TRAVERSII, n. sp. à 
This is a very marked species, easily distinguished by the large quadrate 
centra of the vertebríë, that always show a tendency to split into four parts in 
the line of the venous foramina, and а constriction of the lateral border. 
No. 5a.— Nine cervical vertebre, much water-worn, but showing the 
