MORPHOLOGICAL REVISION 



81 



face is curved and directed largely toward the inner side of the bone. The whole 

 bone is much more clumsy and ill formed than that of the Pelycosaurs (fig. 27, U). 



The pelvis (plate 7, fig. 7) is somewhat distorted by pressure in No. 4684 Am. 

 Mus., and the description is taken largely from No. 1075 Univ. Chicago. The 

 ischium and pubis are broad, flat plates lying horizontally in the body; they are 

 closely united with each other and with the bones of the opposite side. The symphy- 

 sis is marked by a rather prominent but low keel (fig. 29, A and C). It is thicker than 

 it appears on the outer surface, for the contiguous portions of the pubes and ischia 

 of the two sides are much swollen, but the thickening due to this is largely shown on 

 the upper surface. This condition is best shown in specimen No. 4848 Am. Mus., 

 fig. 29, B. The anterior edge of the pubis is much broader than the posterior end 

 of the ischium, so the pelvis is wider anteriorly. The exact position of the pubic 

 foramen can not be determined. 



The portions of the ischium and pubis concerned in the acetabulum stand 

 almost at right angles to the rest of the bones, so that there is a prominent angle on 



Fig. 28. — Three views of the right humerus of Diadrctes sp. No. 4380 Am. Mus. x J- 

 a, posterior view; b, anterior; c, inner. 



the outer side of the pelvis. The ilium rises almost vertically, the shaft is propor- 

 tionally rather stout and the upper end thin and extended to the rear in a blunt 

 point. In specimen No. 4684 the shaft remains quite thick nearly to the upper end 

 and then is suddenly pinched in forming a sort of shelf strongly suggestive of the 

 attachment of a plate over the ilium, but no trace of any such plate has been found. 



The cavity of the pelvis looks particularly narrow and Pelycosaur-like in the 

 mounted specimen, No. 4684 Am. Mus., but this is largely due to crushing. Speci- 

 men No. 4373 Am. Mus. shows a pelvis that has been preserved without distortion 

 of the cavity (see plate 9). 



A pelvis in the museum of the Alte Akademie in Munich shows a distinct 

 facet for a prepubis; this has not been noticed in any of the specimens in the 

 American collections (see figure 6, plate xili, in Broili (5). 



The femur (plate 6, figs. 4 and 5) resembles that of Dimetrodon, but, as in all 

 the limb bones, it is shorter, stronger, and more clumsy of build. The articular 

 face of the proximal end is nearly flat; it covers the end and descends somewhat 

 on the outer surface. The anterior face of the upper end is concave and the inner 



