PERMIAN VERTEBRATES 717 



absence of animals of any great size as compared with the Texas 

 forms. 



Skull. — The skull is represented by two nearly perfect maxillaries, appa- 

 rently the bones from the two sides of the same specimen, and several frag- 

 ments showing the occipital condyles. 



The premaxillaries are similar to those of Dimetrodon and of Empedias 

 as figured by Cope. The external surface is pitted, and there was evidently 

 a large opening of the external nares. The teeth do not show any great dis- 

 parity in size nor are they chisel-shaped ; there is no evidence of the presence 

 of a diastema as in the Pelycosauria in general, but this may be due to the 

 imperfection of the bone. Plate III, Figs. 2, a and b. [No. 6536.] 



The occipital condyles are well rounded, hemispherical in outline, the 

 upper edge being slightly concave, and marked by a pit near the upper edge. 

 [No. 6537.] 



VertebrcE. — There are a great man}' vertebrae, either isolated specimens 

 or small lots belonging together; the majority evidently belong to one or the 

 other of the three species of Clepsydrops described. There are two lots that 

 seem different from the others. 



Two vertebrae very much larger than the others apparently belong to the 

 lumbar or posterior dorsal region. They are characterized by the breadth of 

 the centrum as compared by its height. The lower surface is marked by a 

 rounded but prominent keel. One shows measurements corresponding very 

 closely with those given by Cope for C. natalis from Texas. It is very pos- 

 sible that they represent this species. [No. 6538.] 



A second set of vertebrae resemble in large measure those of Lysorhophits 

 tricarinatus in the free articulation of the neural arch to the centrum and the 

 general form of the centrum ; they differ, however, in the absence of the 

 strongly marked keels and the deeply incised fossae between them. They 

 vary greatly in size, some being as large as those of L. tricarinatus and 

 others three or four times as large. If it were not for the presence of verte- 

 brae of different size they might be regarded as dorsals of the described 

 species. As it is, they seem to indicate a possible new species. 



MEASUREMENTS. 



" Length of a centrum - - - - - .01 i m 



Breadth of a centrum - - - - - .011 



Length of a second centrum ----- .007 



Breadth of a second centrum - . _ .006 



Plate II, Fig. 13, a, b, and c. [No. 6529.] 



Scapula. — There are many incomplete scapulas in the collection. They 

 are all of small size, but resemble in form those figured by Cope (Proc. Am. 



