DISSOROPHUS COPE 529 



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

 Their surface 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, forming 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 surface of the spinal expansions is visible. 



Vertebrae. — Not many of the vertebrae are preserved, and such as 

 are, are not in the best condition. They do not seem to differ from the 

 vertebrae of Cacops in any essential respect. The vertebra con- 

 nected 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 Aspido- 

 saurus or Euchirosaurus. The under surface of the more posterior 

 expansions is shown characteristically in Broili's figure (Paleonto- 

 graphica, LI, PL V, Fig. 56). 



Scapula. — The scapula of Dissorophus differs markedly from that 

 of Cacops in its greater robustness and in its more upright position. 

 The posterior border is thickened and has a more pronounced con- 

 vexity near its middle. The preglenoid facet is very prominent as a 

 sharp ridge, immediately below which is the opening of the infra- 

 glenoid or supracoracoid canal and, close by, back of the lower part 

 of the same facet, is the opening of the glenoid canal. The ridge con- 

 tinuous with the preglenoid facet is less prominent than in Cacops; the 

 post-glenoid part, or metacoracoid, is more extensive, the concavity 

 between it and the hind border of the shaft is deeper. On the inner 

 side the deep fossa into which opens the supraglenoid and infraglenoid 

 canals is deeper and shorter, and the epicoracoid portion is much 

 broader below and internally to this fossa. The opening for the 

 glenoid canal on the inner side, as in Cacops and Trematops, is opposite 

 the lower part of the fossa. 



The three glenoid foramina or canals, which I have called the 

 supraglenoid, glenoid, and infraglenoid, appear to be characteristic of 

 the rhachitomous amphibians, if not of the temnospondyles. I have 



