130 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 



As Lydekker has pointed out ('94, 46), the most characteristic feature 

 of the pelvis is the fact that the ilium and ischium have their long axes 

 more nearly in the same straight line than is the case in the Pampean 

 genera, and this reduces the vertical diameter of the sacro-sciatic foramen. 

 Despite this difference, the pelvis is thoroughly glyptodont in appearance 

 and structure ; the ilium has a rather broad, antero-posteriorly compressed 

 peduncle, expanding into a moderately wide anterior plate, which presents 

 forward and is indistinguishably fused with the sacrum ; the crista is not 

 much thickened and does not display the rugosities for the support of the 

 carapace, which are so strikingly shown in the larger and later genera. 

 The ischium has a slender, laterally compressed peduncle, expanding be- 

 hind into a very large vertical plate, which rises dorsally well above the 

 level of the sacrum and ends in a thick, rugose border for the support of 

 the carapace ; apparently, there is no tuberosity. The acetabulum is large 

 and deeply concave and has a small, deep and nearly circular pit for the 

 round ligament, which partially divides the articular surface into two 

 parts, a large anterior portion and a narrow posterior prolongation. The 

 pubis is a slender, laterally compressed rod, which is relatively longer and 

 thicker than in Sclerocalyptus and much less reduced than in Glyptodon. 

 As in the Pampean genera, the pubis arises from the inner sid-e of the 

 ilium in a very characteristic fashion. I have seen no specimen in which 

 the pubis is quite complete, and it is therefore impossible to determine 

 whether the two formed a symphysis ; apparently they did not, for the two 

 bones diverge ventrally, though there may have been a narrow cross-con- 

 nection, as in Glyptodon. Near the proximal end of the pubis and some- 

 what above the level of the acetabulum, arises a very prominent, rugose and 

 hook-like process, which, according to Burmeister, is peculiar to this order, 

 but occurs also in some of the Santa Cruz Gravigrada. The obturator fora- 

 men is long and very narrow, but relatively not longer than in Glyptodou. 



The femur (Plate XXVI, fig. 6), as has been pointed out by Ameghino 

 ("94", 170) and Lydekker ('94, 46), differs decidedly from that of the 

 Pampean genera and retains considerable resemblance to that of the 

 armadillos ; among the former, it is the femur of Sclerocalyptus which most 

 resembles that of the present genus, which is true of the other limb-bones 

 also. The head is small, sessile, not very strongly convex, presenting 

 proximally rather than inward, and inclined slightly forward ; the sulcus 

 for the round ligament is a shallow pit on the postero-internal side of the 



