636 PR »F. H. G. SEFLEY CN [ A llg. I9OO, 



from the pubis, and the straight longitudinal suture, equally long, 

 which divides it from the bone of the opposite side. Both the 

 posterior and external borders of the ischium are concave ; and 

 the antero-posterior measurements internally and externally are 

 similar, so that the approximation in form is rather towards 

 Pareictsaurus than Procolophon. An external lateral area, concave 

 from above downward, is defined by a thickened ridge which 

 strengthens the bone and extends backward. It is shorter from 

 front to back than in Dicynodon leoniceps, in which all the pelvic 

 bones are anchylosed together. The ischium moreover approximates 

 in type to Procolophon, but in that genus also the anterior margin 

 of the bone terminates superiorly in a point. The pelvic acetabulum 

 excavates the bone concavely in front, being defined by posterior and 

 anterior ridges, more on the type of Phocosaurus than of Dicynodon, 

 though without the superior wedge on the ilium to support tho 

 head of the femur, which Phocosaurus possesses in common with 

 some Theriodonts. The acetabular surface of the ilium has the 

 bone greatly thickened on its internal border, and the thickening 

 recedes from the pubic articulation, so as to define a thin concave 

 area in front of the mass of the bone. It' this thin portion were 

 absorbed, a large transverse obturator-foramen would appear, which 

 would bring the pelvis into easy comparison with the pelvic bones 

 of Plesiosauria. This transverse union between the ischium and 

 pubis is the character which seems of greatest value in illustrating the 

 affinity of the pelvis with that in Procolophon. The most distinctive 

 feature, however, is in the prominence of the thin concave posterior 

 border of the bone in this fossil, which lies between the longitudinal 

 median suture and the thickened posterior angle of the bone. 



(c) The Pubis. (Fig. 5, p. 635.) 



The pubis is not quite so wide as the ischium, and is about half 

 as long from front to back. The bone is remarkable for its short- 

 ness from front to back, in which character it agrees with other 

 Anomodonts, and especially with Procolophon, though the transverse 

 width of the bone is relatively much greater than in Procolophon. 

 There appears to be a thickening of the anterior margin of the 

 bone, but whether that is a normal character is not demonstrated by 

 the evidence available. The relative narrowness of the pubis, as 

 compared with the ischium, has the effect of throwing the blade of 

 the ilium forward. 



The Hind-Limb. (Fig. 6, p. 638.) 



There is little difference in length between the humerus and the 

 femur, which is equal to the length of four or four and a half 

 vertebrse. The fore-leg is relatively and actually a little shorter 

 than the fore-arm. 



The Monotreme characters of the bones are rather more con- 

 spicuously developed in the leg than in the arm ; for though the 



