THE OSTEOLOGY OF THE DIADECTIDAE 



145 



interlocking sutures with clavicles. The posterior process is con- 

 tinued backward, gradually narrowing to a point. Fig. n is a 

 photograph of the interclavicle of a larger specimen (No. 1079), but 

 shows the character of the surface and the connections with the 

 clavicles. 



The vertebra. — Speci- 

 men No. 1077 consists of 

 the two sacral vertebrse and 

 seven presacrals. They are 

 much larger than any of the 

 specimens in which the 

 skull is preserved. The 

 whole series is characterized 

 by the great width of the 

 neural arch compared with 

 the antero-posterior diame- 

 ter. The neural spines are 

 short and stout ; the centrum 

 is simple and deeply bicon- 

 cave; there are no intercen- 

 tra preserved. The ante- 

 rior one of the seven pre- 

 sacrals is free from the 

 others and very perfect, so 

 that I have selected it as 

 characteristic of a mid- or 

 posterior dorsal. The ante- 

 rior and posterior faces of the centrum are round and deeply concave, 

 and it is perforated by the notochordal foramen. The lower edge of 

 the centrum is slightly concave from before backward, and is without 

 any median keel. The neural arch is anchylosed to the centrum, and 

 there is no trace of the suture. As shown in Figs. 12-14, the anterior 

 and posterior zygapophyses are far above the neural canal. The 

 articular faces are almost flat, but are inclined slightly toward the 

 median line, so that the anterior ones look inward as well as upward, 

 and the posterior ones outward as well as downward. The pos- 

 terior face is considerably higher than the anterior. Both faces are 



Fig. 11. — Ventral surface of an interclavicle 

 of a larger specimen than No. 1075 — No. 1079. 



