Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/55

Rh the others more oval. the more anterior are sub-triangular, and the rib pits on the first dorsals are sub-round or vertically oval. Thus the heads of the ribs also vary. The shafts arc all flat, probably more so from pressure. They are frequently curved in the direction of the compression, which suggests a vertical head. They however are probably more or less distorted, and the plane of compression changed. No well defined distal extremity of a rib can be made out, nor have anything like abdominal ribs been preserved.

The scapular arch is remarkable for its large clavicles (or procoracoids). As preserved, the latter are quite convex downwards both antero-posteriorly and transversely, while the coracoids are equally concave in both directions.



The clavicles have a remarkable external flat projection, which is separated from the glenoid cavity by a deep sinus. The glenoid cavity is hounded by an elevated ridge, which sends a branch along the claviculo-coracoid suture to the precoracoid foramen. This foramen is relatively of small size, and is a longitudinal oval; the two are separated by an isthmus composed equally of processes of clavicle and coracoid. The coracoids are very thin except in a transverse