144 



E. C. CASE 



coracoids, and their union in the median line, made a strong ventral 

 covering to the thoracic region not unlike that of Procolophon. 



The cleithrum. — The posterior portion of the upper edge of the 

 scapula is bordered by a short bone which is wider posteriorly and 

 narrows to a point anteriorly. It is anchylosed to the scapula, but 



posteriorly the division is 

 marked by a deep groove. 

 The form is best seen in 

 Fig. 2. Its anterior edge 

 touches, but does not 

 articulate with, the scapula. 

 This bone is evidently the 

 cleithrum. It has much 

 the appearance of the same 

 bone in Pareiasaurus and 

 the scapula figured by 

 Broili, mentioned above, 

 and is in about the same 

 stage of degeneration. 



The clavicles. — The cla- 

 vicles do not meet in the 

 middle line, but are sepa- 

 rated by the interclavicle, 

 with which they are closely 

 articulated by strong sutural processes. Cope speaks of the sym- 

 phasis of the clavicles behind the interclavicle, but this is an impossi- 

 bility in the Diadectidae, as will be seen from the description and 

 figures of the interclavicle. Viewed from above, the clavicles plus 

 interclavicle have the form of a narrow horseshoe, the anterior 

 end of the clavicles being wide and narrowing gradually to a point 

 at about the posterior one-fourth of the scapula. The upper surface 

 of the clavicles is quite flat. Viewed from the side, the anterior 

 portion of the clavicles is broad, but rapidly narrows to an edge 

 which disappears behind the cleithrum. 



The interclavicle. — This bone is somewhat T-shaped. Its form 

 is best seen in Fig. 10. The middle of the anterior end is slightly 

 concave and rounded. Laterally the wing-like sides unite by strong 



Fig. io. — Ventral view of the shoulder girdle 

 of No. 1075. e/ = clavicle, intcl = interclavicle, co = 

 coracoid, ^>c = precoracoid, h = humerus. One- 

 half natural size. 



