INSECTIVORA OF THE SANTA CRUZ BEDS. 



377 



FIG. 36. 



processes of the sacrum. The ischium is short and without tuberosities ; 

 it is deeper vertically than in Chrysochloris, though far less so than in 

 Notoryctes, in which the bone is of a totally different shape and is ankylosed 

 with the transverse processes of the sacrum. The pubis is long, apparently 

 meeting its fellow of the opposite side in a symphysis (as is not the case in 

 Chrysochloris] and the obturator foramen is large. One of the greatest 

 peculiarities of Chrysochloris is the reduction of this foramen to two minute 

 perforations, and associated with this is the entire absence of any pubic 

 symphysis, the two pubes being more widely separated than are the two ilia. 

 In Notoryctes also, despite the very large size of the ischia, the obturator 

 foramina are very much reduced. In short, both the African and the 

 Australian genus have curiously modified pelves, 

 though modified in entirely different fashion in each 

 case, while the pelvis of Necrolestes is of the normal, 

 undifferentiated insectivorous type. 



The femur, as Ameghino has pointed out, is extra- 

 ordinarily peculiar, though not without a certain 

 resemblance to that of Chrysochloris. The head is 

 small, hemispherical and set upon a very short neck, 

 presenting obliquely inward and forward, so that the 

 head is invisible when the bone is viewed from 

 behind ; the pit for the round ligament is exceed- 

 ingly minute. The great trochanter is a thin, com- 

 pressed ridge, which also presents forward as well 

 as outward, with the digital fossa quite obsolete. The second trochanter 

 is a small, compressed, pyramidal projection, and is connected with the 

 great trochanter by a rough ridge, while the third trochanter is hardly 

 more than indicated. The femoral shaft has its proximal position much 

 twisted ; it is broad transversely, and compressed antero-posteriorly, 

 while the distal portion of the shaft is very slender and of cylindrical 

 shape. The distal end is moderately widened and the rotular trochlea 

 is very broad and shallow, almost plane transversely, in fact. The con- 

 dyles are very small, hardly projecting behind the plane of the shaft, and 

 they are quite widely separated from each other. 



In Chrysochloris the femur is not altogether dissimilar to that of 

 Necrolestes, but differs in many respects. The head is conspicuously 

 larger and presents less forward ; the great trochanter is thicker and there 



Necrolestes patagon- 

 ensis, left femur, x \. 

 a. Front view. b. Hind 



view. 



