MORPHOLOGICAL REVISION 



117 



The dorsal surface is rather deeply pitted, the depressions rounded or oval 

 with reticulating ridges between them. The under surface is smooth, and 

 appears not to have been underlaid with lateral expansions of the spines. 

 Back of this shield, on the under side, there are nine spine dilatations, the 

 first six or seven complete in the specimen. They are thin, flat plates, 

 apparently co-ossified with the rather slender spines above, directed nearly 

 transversely, with a less angle of declivity than has the nuchal or scapular 

 shield. The outer extremities are narrowed or obtusely pointed, their upper 

 surface beveled both in front and behind for the dorsal shields. Their sur- 

 face is smooth throughout. 



"The dorsal shields are rather stout, elongate bones, rounded on their 

 outer extremities, pitted on their dorsal surface like the nuchal shield, form- 



FiG. 45. 



A. Dissorophus (Otoccelus Ustudineus). No. 4343 Am. Mus. X J/i. Lower view of thoracic region, 



showing interclavicle, clavicles, cleithra, and scapula. 



B. Same; lower surface of a fragment, showing the femur, tibia, and fibula. 



C. Dissorophus mullicinctus. No. 4593 Am. Mus. X K- Lower view of a portion of vertebral 



column. 



D. Same; upper view of a portion of vertebral column, showing dermal plates overlying and alter- 



nating with the expanded neural spines. 



E. Same; anterior view of same fragment shown in C and D, showing the relation of dermal plates to 



neural spines. 



ing a rather uniform arc of a circle, with less steepness on the sides than 

 that of the nuchal shield. These shields, thick in their middle line, thinned 

 along their anterior and posterior margins, leave a space of from two to 

 four millimeters between their adjacent borders, in which the smooth sur- 

 face of the spinal expansions is visible. 



" Vertebrce: Not many of the vertebrae are preserved, and such as are, 

 are not in the best condition. They do not seem to diflter from the vertebrae 

 of Cacops in any essential respect. The vertebra connected with the first 

 dorsal spinous expansion has the proximal end of the ribs attached. It is 

 broad and flat, articulating with the transverse process and hypocentrum 

 like the early ribs of Cacops. The ribs evidently had no uncinate projections 

 like those of Aspidosaurus or Euchirosaurus. The under surface of the more 

 posterior expansions is shown characteristically in Broili's figure {Paleonto- 

 graphica, li, plate v, 5^). 



