78 
PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
than in Protypotherium. The radial articulation is an almost plane sur- 
face. The styloid process is proportionately shorter and the articular 
surface for the cuneiform flatter than in Protypotherium. 
The manus is unknown. 
The pelvis is known from several fragments, the best preserved speci- 
men (No. 15,093, PI. II, fig. 14) being an incomplete right half, retaining 
portions of the ilium and ischium, with the pubis broken off at the inferior 
margin of the acetabular cavity. Compared with the pelvis of one of the 
larger individuals of Protypotherium australe , the gluteal surface of the 
ilium is seen to be less deeply excavated and the posterior inferior spine 
less prominent. The inferior iliac margin is broad and flat, separated 
from the gluteal fossa by a sharp ridge trending forward from the origin 
of the rectus femoris muscle. In Protypotherium the area thus inclosed 
is rendered concave by a median groove. The ischial spine is large and 
the ilio-pectineal eminence quite prominent, while in Protypotherium it is 
scarcely indicated. The acetabulum is larger than in the latter genus and 
the cotyloid notch somewhat wider. Internally, the surface for articula- 
tion with the auricular process of the sacrum seems to extend farther for- 
ward than in Protypotherium. 
The femur (PI. II, figs. 8-10) differs from that of Protypotherium in 
proportion rather than in detail. The head is globular, with a well-marked 
pit for the ligamentum teres (not shown in the figures), which varies in 
distinctness and depth in different individuals. The great trochanter rises 
above the head about as far as in Protypotherium, but is separated from it 
by a somewhat wider notch. The digital fossa is much wider than in the 
last named genus. The trochanter minor and third trochanter occupy the 
the same relative positions as in Protypotherium , but the third trochanter 
is proportionately larger. Bistally, there is scarcely any difference between 
the two genera in the details of the condylar surfaces. 
The patella (PI. II, figs. 11, 12) is an elongated element of oval shape, 
tapering gradually to a rounded apex. The anterior surface, which is strongly 
convex in all diameters, is quite rugose. The posterior surface is divided 
by a median ridge into two approximately equal, concave articular surfaces, 
extending to the apical extremity, but separated from the upper edge by a 
narrow, roughened area. 
The tibia and fibula (PI. II, figs. 1, 2) are firmly coossified both proxi- 
mally and distally. The two condylic surfaces for articulation with the 
