Il8 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



'^Scapula: The scapula of Dissorophus differs markedly from that of 

 Cacops in its greater robustness and in its more upright position. The pos- 

 terior border is thickened and has a more pronounced convexity near its 

 middle. The preglenoid facet is very prominent as a sharp ridge, immedi- 

 ately below which is the opening of the infraglenoid or supracoracoid canal 

 and, close by, back of the lower part of the same facet, is the opening of 

 the glenoid canal. The ridge continuous 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 infra- 

 glenoid 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 cleithrum or supraclavicle is a much heavier but more slender 

 bone in Dissorophus than in Cacops. It lies, as in that genus, loosely over 

 the top of the scapula, not suturally united with it, arching roof-like over 

 the top. In front it descends over the rounded superior anterior angle of 

 the scapula, fitting into a depression of that bone. Below, it unites by a 

 long oblique suture with the upper end of the clavicle, extending as a narrow, 

 anteriorly curved process quite to the place where the coracoid turns inward, 

 that is doubtless to the sutural line between scapula and coracoid. 



" Interclavicle: The interclavicle is a broad, gently concave, and thin 

 bone, resembling that of Cacops, but larger and broader. It has a rounded, 

 thin border anteriorly, and similarly rounded, thin lateral margins. _ Pos- 

 teriorly the bone is broken away, but the thickened median part indicates 

 a posterior median extension, probably as in Cacops. 



''Clavicles: The clavicles are large, broad, smooth bones, meeting each 

 other in the middle line, and covering, for the most part, the interclavicle. 

 They are convex below, with their greatest expansion some distance away 

 from the middle. In the position in which the girdle now is, evidently the 

 normal one, the cleithral ends are directed vertically upward, nearly parallel 

 to each other, with an interval of a little more than two and a half inches 

 between their upper extremities, which are suturally and closely united to the 

 lower ends of the cleithra or supraclavicles. The upper extremity is much 

 stouter and broader than is the case with Cacops. 



"Upon the whole, the pectoral girdle, both primary and secondary, is 

 remarkable for its stoutness and firm articulations. 



''Humerus: Of the two humeri, the left is preserved completely save 

 the capitellar angle, while the right has the lower end perfect with the upper 

 extremity wanting. In the figures the capitellar portion has been reversed 

 from the right side. In general shape and structure the bone resembles that 

 of Cacops closely, so closely that there may be difficulty in distinguishing 

 them in ill-preserved specimens. The humerus of Dissorophus is distinctly 

 stouter, with the ends a little more expanded and the lateral curvatures a 

 little deeper; the entepicondylar expansion is stouter. 



"femur: The right femur is preserved in pretty good condition, save 

 the external condyle and a part of the lower portion of the crest. _ Its resem- 

 blance to the femur of Cacops is close, but, like the humerus, differs in its 

 greater stoutness. The adductor crest is heavier, and not as deep; the shaft 

 is distinctly stouter. The articular surface for the tibia is rather better 



