Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/785

 sible to make out the parts, or to say whether or not they are provided with the long characteristic spinous processes of P. Speneri. Indeed it is difficult to determine the number of joints, though twelve can be counted. As, however, there are fourteen or fifteen pairs of ribs, there must be at least as many dorsal vertebrae. It would still seem, nevertheless, that they are not so numerous in this species as they are in P. Speneri, in which we have seen there are seventeen or eighteen dorsal vertebrae. But it is quite possible, indeed it is likely, that there are more ribs than we have been able to enumerate, in which case we have underestimated the number of the vertebrae ; and the two species may be found to agree in this particular more closely than is apparent. It is equally impossible to ascertain the character and exact number of the cervical vertebrae ; but as six or seven lie scattered about in front of the trunk, it would seem that this species may have seven, the number of the neck-vertebrae of P. Speneri according to Meyer. All that can be said about the caudal vertebrae is, that the traces of their remains seem to indicate that the tail, when perfect, must have been of considerable length. About 2 inches of the distal extremity is determinable ; and as about the same length of the proximal portion seems to be broken away, the tail, when complete, must have been longer than the trunk, which is nearly 3-1/2 inches in length.

The ribs lie, as we have already said, spread out in their natural order on each side of the vertebral column, and fourteen or fifteen pairs can be enumerated ; but there is some difficulty in determining the precise number. They are well and regularly arched from end to end, and are moderately and nearly equally thick throughout. Towards the proximal end they are a little flattened, and terminate in a slightly enlarged simple head of a triangular form. The distal extremity is abruptly truncated, but is not flattened and widened to the same degree as the ribs of P. Speneri ; neither are the ribs so decidedly grooved as they are in that species, but are, on the whole, more cylindrical. The ventral ribs appear to have been numerous and comparatively stout ; they lie pressed in between the vertebral ribs near to the spinal column, but their relative number cannot be ascertained. The longest vertebral ribs are near the centre of the trunk ; here they are 7/8 inch long, measured along the chord ; they shorten a little before and behind to about 7/10 inch in front and 4/10 behind.

Both the coracoids are well preserved, particularly the left, which lies nearly in its natural position at the left side on the fore part of the trunk. The right coracoid is removed a short distance in front. They are stout discoidal bones 5/8 inch in diameter, with a deep, wide notch, apparently on the posterior margin, forming the glenoid cavity for the articulation of the humerus. At the inner margin of the notch there is an elevated boss ; and from thence to the front margin there is a widish ridge indicating perhaps the compound nature of this bone, which is most likely composed of both the coracoid and scapula, the glenoid cavity being as usual at the junction of the two elements ; but there is no distinct trace of a suture. There is a

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