Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/52

48 The end of the muzzle was broken from a part or the whole of the cranium, which has not been rediscovered, though Dr. Turner has made careful search. It was found in front of the vertebrae here regarded as cervical, at some distance from them.

The whole skeleton has been under considerable pressure, so that most of the ribs have been pressed flat on the vertebræ; the long parapophyses of the cervicals have most of them been fractured at their bases and compressed, those of opposite sides thus approaching more nearly in the form of chevron bones than they otherwise would have done. The proximal cervicals are obliquely flattened by the pressure; the other cervicals have the bodies naturally flat, with the articular surfaces much less so than the median portion. Some of the caudals are obliquely distorted.

Description-Vertebræ.-''The neck may be safely assumed as a point of departure, as it consists of above sixty mostly continuous vertebræ, which graduate to an atlas of very slender proportions. Most of them preserve more or less developed parapophyses. At the posterior extremity of this series, sixteen are perfectly continuous, and in this portion a great gradation in form is apparent. The anterior are narrow, compressed, and similar to the more distal cervicals in the elevated position of the lateral angle; the anterior are subquadrate, thick, and with lower lateral rib, and stronger ?pleurapophysis. In these respects the latter resemble the dorsals which follow, towards what I believe to be the tail. Four anterior dorsals are in one mass (figured in plate 3); in this series the lateral angle first approaching, is finally lost in the margin of the rib-pit, the posterior thus resembling other dorsals. There can be so far little doubt that the anterior and posterior extremities of the masses are correctly interpreted.

In a series of four anterior dorsals, which like the preceding, are in their original continuous mass, those of one extremity have contra rounded in section, with inferior rib-pits; those of the other have quadrate centra and elevated diapophyses; the former have the character of the first dorsals, the latter of the median dorsals. The posterior dorsals and anterior caudals form in like manner a continuous series of eleven vertebræ, fractured in four places. In them the diapophyses steadily descend, reaching the inferior plane in the last, thus with the reduction of the venous foramina to one, at the seventh, indicating the point of transition from dorsal to caudal series. The zygapophyses preserve the usual arrangement, but are much compressed, so that the posterior or down-looking, are confluent, and scarcely separated by an emargination.

The neural spines at their bases have a slight posterior obliquity, and the superior portion leans strongly in the anterior direction. The inferior limbs of the cervical pleurapophyses appear to be entirely wanting. The articular faces for the chevron bones are seen at the extremity of the inferior rib of the caudal.

Of the cervicals there are both axis and atlas. Of the caudals, probably the distal half, at least, is lost. A single vertebra near the middle does not relate to either of those anterior or posterior to it. There are, therefore, at least four lost from that region also.

There is a considerable interruption immediately anterior to the last dorsal vertebra. Three large vertebræ, with long diapophyses, belonging here, were imbedded in the hard matrix which protected the pelvic arch. These are far from relating immediately to the vertebra preserved before and behind them. I estimate the number missing as follows: Seven of the fourteen dorsals preserved have more or less elongate diapophyses. In the Plesiosauri, vertebræ of this character, are much more numerous ; in P. homalospondylus Owen gives seventeen. If we add ten to the series in the present species it will give the abdominal space between the adjacent margins of the o. o. pubis and coracoidea an extent eqnal to the length of the pelvic arch. This is relatively shorter than in the Plesiosanri. Dr. Turner found that a space of "three or four" feet intervened between the two portions of the skeleton, which was otherwise continuous. I think ten an average number to represent safely the missing dorsals.

From the cervical proximal regions probably three vertebra are missing from two interruptions. The remainder of the cervical series exhibits three interruptions. Most of the proximals have been broken medially, leaving the ticulations solid, an advantage in determining their continuity. Three vertebræ and one-half are thus found to be missing in this region.

The whole number of vertebræ preserved and lost, with the relative lengths of each, may be stated as follows: