EOSTKEN LTBYCA. 
215 
condyle (i.c.) is greatly developed and is directed backwards; its lower end is about on 
a level with the lowest point of the trochlea, a condition not seen in other Sirenia. 
The proximal end of a large humerus perhaps belongs to this species. In this 
specimen the head is strongly convex in all directions and somewhat oval in outline ; 
its edge forms a projecting rim. The tuberosities are worn, but it can be seen that 
the outer was the largest, and that there was a small bicipital groove. 
In many respects the humerus of Eosiren resembles that of Mceritherium, the chief 
points of similarity being the form of the distal trochlea and of the inner condyle, and 
the arrangement of the deltoid crest ; on the other hand, in Moeritherium the humerus 
is relatively longer and more slender, and the supinator crest is strongly developed. 
Hind Limb. — A right os innominatum (text-fig, 68, B) was found associated with the 
anterior portion of a skull and the vertebrae described above. This specimen is of 
great interest, as showing in some respects a degree of reduction intermediate between 
that seen in the pelvis of Eotherium (text-fig. 68, C) lately described by Abel * and that 
found in Ilalitherium schinzi (text-fig. 68, A), though approaching much more nearly the 
form of the latter. The bone, as a whole, is considerably abraded, so that many details 
of structure have been obliterated. The ilium (^7.) is roughly trihedral in section for 
some distance in front of the acetabulum, and further forwards still it expands some- 
what, becoming a little flattened from within outwards. The outer convex face is 
traversed by a slightly marked ridge running from the anterior point to the anterior 
angle of the rim of the acetabulum. The inner face of the anterior end is somewhat 
flattened and probably was in contact with the end of the sacral rib. Immediately in 
front of and above the acetabulum there is a roughened prominence, apparently the 
point of origin of the rectus femoris muscle. No trace of an ilio-pectineal^tubercle 
is preserved. The ischium {is.) is a broad bar of bone, expanding a little towards 
its somewhat thickened distal end, which is sharply truncated by a surface looking 
inwards and backwards ; its upper and lower borders are both concave, the latter most 
deeply so ; the outer face is divided by a slight ridge running from the posterior angle 
of the acetabulum to the ischial tuberosity into a narrower dorsal portion and a much 
wider ventral region. The pubis {pu.) is represented by a large triangular process, the 
anterior border of which rises just opposite the lower angle of the acetabulum. The 
posterior border forms a continuous curve with the lower edge of the ischium. There 
is no descending process of the pubis or ascending process of the ischium, so that 
there is no complete obturator foramen, the whole of the lower and posterior borders 
found in the ordinary mammalian pelvis and still persisting in Eotherium (Abel, op. cit. 
p. 191) being wanting. At the same time the remnants of the pubis and ischium 
so far as they go approach rather more nearly the normal form than is the case in 
the later Ilalitherium (see also supra, p. 119). The oval acetabulum is well developed, 
with a prominent border ; the acetabular notch {a.n.) is situated as in Eotherium. 
* Abel, op. cit. pp. 187-195, pi. vii. fig. 1. 
