622 
Kia. d.—Iff/amodon cruentus ; Left os in- 
nomiiiatuiii, J natural size. 
THE OSTEOLOGY OF HYJ5N0D0N. 
VI THE HIND-LIMB. 
Tl„ /.Ms of Hysrnodon i» not otpociolly croodont in character approximating- 
more the^condition round in certain of the Carnivora. In the earlier and less dif- 
ferentiated creodonts, as likewise m the insec- 
tivores, the ilium is more or less distinctly 
prismatic and trihedral in shape, while in 
Hyanodon it is flattened and expanded into a 
plate, though less so than in some of the re- 
cent large genera. So far, complete specimens 
of the pelvis have been found only in H. cru- 
which will therefore be used as the basis 
for the present description. Fragments be- 
longing to some of the other species indicate 
that certain differences obtain between them 
regarding the shape of the ilium. In H. crti- 
entus the neck of the ilium is short, deep, and 
thick ; the ischial border rises abruptly to form 
a quite moderate anterior expansion, with a 
somewhat concave gluteal surface. The rugose area for the attachment to the 
sacrum is placed very far back, its posterior margin coinciding with the commencing 
expansion of the iliac plate. The latter thus extends considerably in front of the 
sacrum and, when viewed from the side, almost completely conceals the last lumbar 
vertebra, against the transverse process of which the ilium partly rests. The iliac 
surface is quite broad posteriorly and somewhat oblique in position ; anteriorly it 
becomes narroAver. The acetabular border describes a slight curve, with the con- 
cavity downward, which is much less pronounced than in Canis, but decidedly more 
so than in the cats or mustelines. The pectineal process, which among the creo- 
donts is so generally well developed and prominent, is in Hycenodon reiu'esented 
by a mere tubercle. The acetabulum is quite large and deep, and its articular sur- 
face is but little reduced by the sulcus for the round ligament. 
The ischium is rather short, compressed and plate-like. It does not lie in the 
same veitical plane as the ilium, but is posteriorly somewhat twisted upon itself and 
everted, though this eversion and depression are much less marked than in the dogs, 
and the tuberosity is much less prominent and massive than in those animals. 
I he pubis IS short, straight, broad and very thin. The symphysis, formed 
partly by the pubis and partly by the ischium, is elongate. The obturator foramen 
IS a long, narrow oval, with its principal axis directed antero-posteriorly. The 
foramen is considerably more elongate proportionately than in the dogs, which is 
due to tlm greater width o the descending process of the ischium in the latter. 
not a cefd Zt' T ZT border does 
not ascend so abruptly to form the anterior expansion, which is narrower- the 
acetabular border IS less decidedly curved and tbLlni. i 7 
cavated. ^ ^ gluteal surface more deeply ex- 
