13° 



E. C. CASE 



girdles, but in the post-dorsal and lumbar regions the column has 

 sagged down of its own weight, causing a break and slight dis- 

 placement, vertically, of the column. One peculiar effect of the 

 sagging down of the vertebral column is that the ribs of the thoracic 

 region have been bent upward and backward, reversing the natu- 

 ral curvature so that the plates covering them seem to be on the 

 ventral surface. The upper edges of these ribs and the dorsal edge 

 of the scapula stand well above the tops of the neural spines. The 

 dermal plates, which are arranged shingle-wise, were evidently 

 firmly attached together. 



The humeri and femora of both sides are in position. The 

 humeri are extended straight backward and the femora straight 

 forward. This position, in harmony with the undisturbed con- 

 dition of the rest of the skeleton, is important as indicating the 

 natural position of the limbs and the prone position of the animal 

 as it crawled upon its belly. 



As described above, the skull has the lower jaws so fixed that 

 it is impossible to clear the palate completely; but as it is entirely 

 free from any distortion, the external form is perfectly shown. 

 The surface of the skull, as in all of the Diadectidae, is very rugose, 

 and the bones are closely anchylosed together, so that it is almost 

 impossible to trace the sutures between the bones, such sutures 

 as are given having been largely made out from the inferior sur- 

 face of the skull in the less perfect specimens. 



The skull is wide behind and narrows rapidly in the facial 

 region, making the nose relatively thin, in this respect resembling the 

 Pariotichidae. The skull proper is quite depressed, but seems 

 much higher with the lower jaws in position, because of their great 

 vertical extent. The upper surface of the skull is flat and of an 

 elongate heart-shape. The parietal foramen lies near the pos- 

 terior edge, and is not of such great size on the surface as to deserve 

 the adjective "enormous" applied to it by Cope; but the edges 

 of the foramen are beveled on the lower surface, so that the inner 

 opening is two or three times the size of the outer. This is well 

 shown in specimen No. 1078. There is no indication of grooves 

 for the sensory organs. 



Viewed from the side, the skull shows three openings; the exter- 



