| OCR Text |
Show 1888.] ANATOMY OF THE MESOSUCHIA. 439 this position, and formed a buckler covering the back from the neck to the tail, as in Teleosaurus temporalis, with which E. E. Deslongchamps identifies the above-mentioned ' Gavial.' Whilst their imbricated arrangement permitted some gliding of the scutes on one another, and thus gave some degree of flexibility to the trunk, the tongue-like processes must have imparted great security when the limits of this mobility were approached. In their form and in the position of their tongue these scutes differ from those of the Purbeck Wealden Goniopholis. From those of the Wealden Bernissartia they differ in having one and not a double keel, and in having a tongue, which the scutes of Bernissartia want. The skeletons of these Peterborough Mesosuchians, so far as their plan is illustrated by their remains in the Leeds Collection, differ from those of the Eusuchia (1) in the amphiccelous character of all their vertebrae except the two foremost and the two sacral ; (2) in the absence of the largely developed carina which so strongly characterizes the cervical vertebrae in Eusuchia ; (3) their atlas differs in possessing a diapophysis placed on its pleur-apophysis; (4) their epistropheus differs in having a well-developed diapophysis iu the level of its neuro-central suture, and a parapophysis on its centrum. In Gavialis gangeticus I find the capitular and the tubercular costal articulations both placed wholly on the pars odontoidea and the second cervical riblet to articulate exclusively with this. In G. gangeticus, Crocodilus niloticus, and in Alligator mississippiensis I do not find any trace of a diapophysis on the atlantal neurapophysis. In C. niloticus the capitulum of the second rib rests wholly on the pars odont. ; and the tuberculum costae is borne chiefly on this, but to a very small extent also on the centrum of the epistropheus. In another example of this Crocodile the capit. and the tuberc. costae are both wholly borne on the pars odont. In C. americanus the second rib articulates wholly with the pars odont. In Alligator lucius I find the capit. costae resting on the pars odont., and the tuberc. costae articulating with a rudimentary diapophysis situated on the neural arch of the epistropheus just above the neuro-central suture. The plan of the articulation of the second rib is plainly subject to variation in individuals of the same genus and even species. Dr. G. Baur, in an example of Gavialis gangeticus examined by him, found the capitulum only of the second rib articulating with thenars odont.; and a minute diapophysis on the neural arch of the epistropheus, with which the tubercle of the rib was probably connected by ligament. Dr. Baur also found in Alligator mississippiensis the capit. costae articulating chiefly with the pars odont. and by a minute facet with the true centrum of the epistropheus. In Croc, americanus, Scbneid., Baur also found the capit. costae articulating with the pars odont.; and the tuberc. costae touching the neurapophysis of the epistropheus, but without articular facet on this latter (43). These discrepancies and those observed by Koken (44) make it very desirable that these details should be examined in larger numbers of individuals of the same apecies. So far as the |
