466 S. JF. Williston — Restoration of Limnoscelis. 



attached to the under side of the fifth vertebra back of the func- 

 tional sacral, articulating with the fourth. It is long and slen- 

 der. Back of this the chevrons are more or less dilated distally 

 and are long ; on the distal part of the tail they are more slender. 



Large intercentra occur between the anterior caudal verte- 

 brae; one, that articulating between the second and third true 

 caudals, has two small processes on the under side, correspond- 

 ing to the branches of the chevrons ; and all the following 

 chevrons have the proximal end in the form of an intercentrum ; 

 another bit of evidence, if such be needed, that the chevrons 

 are merely outgrowths of the intercentra. 



As regards the structure of the legs of Limnoscelis I have 

 little to add. With one of the feet of specimen 809 Yale 

 University, two small bones are preserved attached to the 

 calcaneum. They are evidently either the third and fourth 

 distalia, or the centrale and a distale, probably the former. In 

 the Chicago University specimen all these four bones are pre- 

 served of one foot ; I have figured them (figs. 19-23). The 

 astragalus differs distinctly from that of the Diadectidae in its 

 smaller size, and more cuboidal shape. Since the discovery of 

 these small tarsal bones in Limnoscelis, it would seem not at 

 all improbable that additional nodules corresponding to the 

 first three distalia, as in Diaspar actus, may yet be found. 



Nor have I much to add regarding the structure of the skull 

 at the present time. I feel confident that I recognize both the 

 tabulare and supratemporal, giving the full complement of cra- 

 nial elements, with the exception of the intertemporal, known 

 only in /Seymouria. I give a figure of the anterior end of the 

 Chicago mandible (fig. 18), showing elongate teeth correspond- 

 ing to those of the premaxillae. The teeth are implanted 

 deeply in sockets, as in Diadectes, and show a deeply infolded 

 dentinal structure. 



The characters of Limnoscelis may be given as follows, 

 omitting all those common to the Cotylosauria of America, as I 

 have recently summarized them :* Limnoscelis — Crawling, litto- 

 ral or subaquatic reptiles, with a rather long body and long tail ; 

 probably bare-skinned. Head elongate, narrowed anteriorly, 

 broad behind, with elongate prem axillary teeth, a single 

 row of conical teeth in maxillae and dentaries ; prefrontal and 

 postfrontal meeting broadly over orbits ; pineal foramen small ; 

 tabularia and quadratojugals present, probably also supra- 

 temporals ; occipital condyle flattened ; basipterygoid process 

 loosely articulated with pterygoids. Twenty-six presacral ver- 

 tebrae, their spines short and not rugose at extremity ; a single 

 functional sacral vertebra, one sacrocaudal and fifty-five or 



* Journal of Morphology, 1912. 



