The anterior pelvic outlet is smaller than the posterior, from the divergence of the ischia pos teriorly ; and the cotyloid cavities are inclined outwards slightly, so as to overhang the femora in the prone position.
The centre of gravity, in these animals, being placed much nearer the anterior than the posterior extremities, the former bear the most of the weight, while the latter act more as impelling agents in the powerful bounds which they execute.
The ilia of the Bear are shorter, thicker, and more massive, with more expanded wings, a better-marked anterior superior spine, and a more marked lumbo-iliac angle ; the ischia short and widely expanded, and the pubes remark ably strong, with a very long symphysis. At the anterior pelvic outlet, the transverse meter is a little larger than the antero-pos terior, and the acetabula are large and deep. In the Badger the ilia and ischia are large, expanded, and curved outwards at their free extremities. The iliac shaft is prismatic, with an ilio-lunzbar ang,le of 140°. The pubes are rather long, with an elongated symphysis, and form an angle with the ilia of about 130°. The same general conformation is evident in the Racoons and Coatis, the ilio-ischial angle being, however, somewhat better marked, and the ilio pubic about 145°. The Coatis have but one sacral vertebra. In the Hymna, also, the iliac wings are considerably spread, with a very pointed anterior spine. In the Dingo the isehio-pubic element is very short, the anterior outlet and obturator foramina small, but the posterior outlet larger. The Weasel has a very small pelvis, with but two sacral vertebrm, one only articulating with upper extremities of the long iliac shafts.
In the Phocw the sacrum has four vertebrm, the first only articulating with ilia, and much wider in its transverse processes than the rest ; the ilia are extremely short, thick, and curved outwards, with very small external fossm; the ischia are long and slender, with small tuberosi ties almost touching the second coccygeal ver tebra, with long rami not forming a symphysis, but directed backward to meet the pubis. The pubes are very long, slender, and oblique, with a short syrnphysis, and including a very large, oval obturator foramen. The pelvis altogether somewhat resembles that of the Badger, with the superior opening much elong-ated antero posteriorly, and triangular in shape, with the base at the sacrum. The shortness of the ilia alone indicates the great contraction of the posterior extremities for their swimming re quirements. Dr. Knox has observed, in a pregnant female Seal, a separation of the symphysis pubis, and elong,ation of its liga ments to the extent of nearly 2 inches, such as Le Gallois has described in the Guinea-pig. He found, moreover, that such a separation of the bones produced much more enlarge ment of diameters in these elongated trian gular pelves than in the transverse oval form of the htunan female.
In the order of pelvic development, the Pachydernzata occupy a very high place, being characterised by great massiveness, propor tionate shallowness, and perpendicularity of pelvis, and large and overhanging acetabula, the better to support the immense weight of these animals, thrown more on the hinder ex tremities than in the Carnivora, from their bulky dorsal structures and abdominal vis cera. The ischial spinous ridges and anterior
inferior iliac spines are faintly marked or wanting, the sacral spines are coalesced into a continuous crest, and there is little or no sacral promontory.
The sacrum of the Elephant (fig. 95.) is comparatively very narrow, flat, and short, and placed on the spine at an angle almost imperceptible ; the number of vertebrm being four only, according to Cuvier. The coccygeal vertebrm are numerous.
The ilia are short, broad, massy, fan shaped, and much expanded, with a large concavity or iliac fossa directed forwards and downwards, the dorsum being alter nately concave and convex. The iliac crest (c) is large and flat-arched, with the anterior su perior spine (a) hooked suddenly downwards, and the posterior inferior directed backward from the sacro-iliac joint, to afford leverage to the powerful sacro-iliac lig,ament. There are no well-marked iliac ribs, except the cotylo sacral (d), which is very strong and massy. The ischia are moderately short, and form an ilio-ischial angle about 145°, presenting no spine, and having the tuberosities (e) directed dorsally, and the rami (f ) vertically towards the abdominal surface. The pubes are short, and directed almost horizontally inwards, with a well-marked ilio-pectineal spine (h). The syrnphysis (g) is parallel to the vertebrm, and very long, including the whole of the short ischial rami as far as the rough por tion forming the tuberosity, so that the ischio-pubic symphysis extends as far back wards as the tuberosities. The sciatic notches are wide and open, but the obturator foramina are smaller than the cotyloid fossm, which are very large and overhang much at the superior or dorsal part. The planes of the acetabula are inclined from the perpendicular about 70° in the elephant, being about 5° more than in the fossil Megatherium and Mylodon. The pelvis of the Elephant is altogether remarkable for its perpendicular position, the lunzbo iliac angle being about 120° only, and the pubes being advanced as far forward as the iliac crest, at an angle of 100° with the ilia. Thus the posterior limbs are brought more under the weight of the animal. The superior outlet is roundish, but broader at the pubes than at the sacrum, and the antero-posterior diameter is but little larger than the trans verse. In the fossil Elephant, however, the antero-posterior diameter is greater in pro portion. The female Elephant has the pelvis more open than the male, and the borders more trenchant,according to Cuvier. Blumen bach states that the round ligament, as well as the cotyloid depression, is wanting in the Elephant.