122 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



orbit. The small size of the parasphenoid in the present genus also explains 

 its apparently entire absence in Trematops, though it is not improbable that 

 the rhinencephalic canal in Trematops, were it preserved complete in the 

 type specimen, would show the remains of the parasphenoid coalesced with 

 it as in Cacops. 



"The maxillary teeth in Cacops are all small and of nearly uniform size, 

 in an uniform closed series. I count about 20, but it is possible there may 

 have been a few more. 



"The mandible is remarkable for its slenderness. Posteriorly it has a 

 broad expansion, but the ramus from the middle of the orbits forward is 

 slender. A deep fossa is present in front of the condyle, and the median 

 symphysis in front is a little expanded. It has apparently the same number 

 of teeth as in the maxillse, and all, like them, are of uniform size. 



" Vertebra: The vertebral column of the mounted skeleton was appar- 

 ently quite complete as it lay in the matrix in association with skull and 

 limbs. In the removal of the thin incrusting matrix, however, a few of the 

 pleurocentra of the anterior vertebrae and some of the small elements of the 

 tail were lost, notwithstanding the most scrupulous care. Of these, only 

 the possible pleurocentra of the atlas and the dorsal elements of the first 

 5 or 6 caudal vertebrae have any morphological significance; future prepara- 

 tions of other skeletons yet contained in the matrix will doubtless complete 

 even these small details. The column as found was continuous from the 

 skull to the tip of the tail, without break, save that the last few caudal 

 vertebrae were slightly angulated from the rest of the series. The presacral 

 vertebrae had a gentle, sinuous curve, with the convexity to the right as far 

 back as the end of the dermal carapace, to the left from thence to the sacrum. 

 There is also a slight vertical sinuosity in the same regions, convex above 

 anteriorly, below posteriorly. These curvatures seemed so normal that 

 no attempt has been made to reduce them in the mounted skeleton, and I 

 have figured the column as it lay. A slight pressure to the left has crowded 

 the ribs upward on that side and downward on the opposite side, but to a 

 very slight extent only. The perfect union of the different elements, at 

 least as far as the beginning of the chevron caudal vertebrae, removes all 

 possible doubt as to their number and relations — 21 presacral, 2 sacral, 6 

 pygals, and 15 or 16 chevron caudals. The spines, save those of the first 2 

 vertebrae, are of nearly uniform length throughout the carapacial series, 

 15 in number, a trifle longer perhaps in the anterior and middle region, and 

 a little more slender in the last 3 or 4. Those of the free presacral vertebrae 

 are progressively shorter and less stout. Throughout the series covered by 

 the carapace they are slightly thickened at the upper end, with the anterior 

 and posterior margins thinned, and with a lateral ribbed thickening on each 

 side near the middle, as though for the support of the terminal expansion. 

 Covering the top of each spine there is a rooflike expansion, wider in the 

 middle and narrowed at each lateral end. Their sides slope downward at an 

 angle of about 45 degrees to the full width of the superincumbent dermal 

 scutes. The anterior margin of these plates is uniformly beveled for articu- 

 lation with the posterior margin of the superincumbent intercalated dermal 

 scute. The posterior beveling is much broader in the middle. Presum- 

 ably these expansions are outgrowths from the top of the spine, carti- 

 laginous in origin, but of this I do not feel entirely assured, since in every 

 case where I have removed them I have found what appears to be a sutural 



