REPTILIA : CLEPSYDROPS 75 



tively smaller and the entepicondylar process is relatively much 

 larger. They also agree well with the specimens referred to 

 Clepsydrops from Illinois. 



Ilium. — Because of the number, shape, and size I refer several 

 ilia to this genus and species, one of which is shown in Plate XXXI, 

 Fig. 2. It has a rather narrow and elongated posterior process. 

 The upper border is much higher and thinner in front than behind, 

 the hind extremity with a small cartilaginous surface. The inner 

 side shows marked rugose surfaces for two sacral ribs; there may 

 have been a third. The outer side has a distinct curved ridge for 

 muscular attachment. 



Ischium. — ^A well-preserved ischium, because of its size, doubt- 

 less belongs with one or the other of the ilia like that just described ; 

 it is shown in Plate XXXI, Fig. 4. It is of the typical pelyco- 

 saurian shape with sharp cartilaginous borders; the blade convex 

 on the outer, concave on the inner, side, with a thick border for 

 the acetabulum. Several small or very small ischia of the same 

 shape are among the collection, but as the ischia of the Permian 

 reptiles in general are very uncharacteristic bones, they can only 

 be referred to this genus doubtfully. 



Quadrate. — ^A very complete quadrate, which because of its 

 size may be provisionally referred to this genus, is shown in Plate 

 XXXI, Figs. 5, 6. The roughened elongated surface on the 

 posterior side for union with the cranial bones is very conspicuous. 

 The condylar surfaces are perfect; the outer elongate part separated 

 from the inner, more triangular one, by a deep groove. 



Articular. — Several articular bones in perfect preservation may 

 belong with this genus. I figure one in Plate XXXI, Figs. 8, 9, 

 showing the characteristic form of the bone; it is of interest as 

 proving the absence of an anterior or prearticular process to the 

 bone; that is, the prearticular bone is distinct. 



NAOSAURUS 



Of the real skeletal structure of Naosaurus, notwithstanding the 

 various restorations that have been published, very little is known 

 aside from the precaudal vertebrae, the pelvis, and perhaps the 



