42 



AMERICAN PERMIAN VERTEBRATES 



of fracture in the specimen. The ischia have an angular margina- 

 tion in the middle, the sides curving outward and upward to the 

 rounded posterior angle. The sutural division between ischium 

 and pubis is at about two-fifths of the length from the front end 

 of the pelvis. The pubic foramen is remarkably large at the 

 bottom of a rather deep fossa situated a little in front of the 

 ischio-pubic suture, and not far from the acetabular border. The 

 acetabulum is deep and large, with an overhanging, nearly hori- 

 zontal roof-like process, at the upper posterior part. In life the 



cavity looked almost di- 

 rectly outward. The ilium 

 is relatively small; it is flat- 

 tened and thinned above 

 and in front, with a rather 

 stout, narrow process di- 

 rected backward and a 

 little outward, nearly hori- 

 zontal. Upon the whole, 

 the structure of the pelvis 

 is nearly identical with 

 that of Diadectes and the 

 Pariotichidae, and even of 

 Eryops and Cacops, save in 

 the form of the ilium; in 

 Diadectes, broader above 

 and produced backward; 

 in the temnospondyls without iliac projections either in front or 

 behind. While there is but a single sacral vertebra in Limnoscelis 

 and Seymouria, in Cacops there are two, a precise reverse of what 

 has often been supposed to be diagnostic characters of these two 

 classes of vertebrates. The femur is of the characteristic Diadectes 

 type, short, stout, and expanded, with a heavy, protuberant tro- 

 chanter, and a large digital fossa. The trochanter has a large facet, 

 20 or more millimeters in diameter, looking backward, and is 

 rugose; the adductor ridge is pronounced and oblique. The tibia, 

 like the femur, is short and stout, with a greatly expanded upper 

 end, and a strong cnemial protuberance. The outer side is deeply 



Fig. 15. — Limnoscelis paludis. Diagram of 

 pelvis, from the side, il, ilium; pb, pubis; is, 

 ischium. 



