6o 



AMERICAN PERMIAN VERTEBRATES 



Pelvic girdle and extremity. — The pelvis has suffered little dis- 

 tortion or displacement, lying below the first two presacral, the 

 sacral, and the first two or three caudal vertebrae. The sutures 

 between the different elements are all rather widely separated. 

 The pubes are subquadrate or trapezoidal in outline, considerably 

 broader at their front border than at the pubo-ischiadic suture. 

 The front border of each is gently convex in outline, and the two 

 are convex from side to side below, without the median keel so 

 characteristic of Limnoscelis. The rather small obturator foramen 



Fig. 21. — Seymouna baylorensis.. Pelvic girdle and femora, from below, one- 

 half natural size, pb, pubis; is, ischium; il, ilium; /, right femur, tibial side, as articu- 

 lated; f, femur of Craddock bone-bed specimen, ventral side, a little more than half 

 natural size. 



is situated not far from the acetabular ischiadic angle. The ischia 

 are very nearly twice the length of the pubes, rather deeply con- 

 cave on the sides back of the acetabular angle, somewhat expanded 

 behind; the posterior border with an undulating outline, but with- 

 out a very pronounced median emargination. In the middle 

 there is a pronounced keel, thickest and broadest about midway 

 of the bones. The ilia are unusually narrow antero-posteriorly 

 between the upper and lower expansions ; they are relatively high. 

 The front border is nearly vertical, gently convex anteriorly above; 

 the upper border is thin, sloping downward and outward to a 

 narrow process posteriorly. The posterior iliac notch is deep and 



