The pelvis of the fossil Mastodon is much less depressed and expanded than that of the Elephant, according to Cuvier, and its outlets smaller, showing that its abdomen was of less size.
The Rhinoceros has four sacral vertebrm, three articulating with the ilia, and supported by articulation with last lumbar transverse processes ; and the caudal vertebrce numerous.
The ilia are large, massy, short, and ex panded, though much less so than in the Elephant ; with the anterior iliac fossa well marked, and the dorsum also generally con cave from side to side, from the backward curvature of the inner border to be applied to the sacrum. The crest is large, and the anterior superior spine turned forwards, as in the Elephant, and forked at the end. The ischia are longer than in the Elephant, with thick tuberosities, turned much outwards. Pubes long, and united at a sharper angle, with prominent ischio-pubic symphysis. The lumbo-iliac angle in the two-horned: variety is 125°, the ilio-ischial 145°, and the ilio pubic 150°, making the pubis nearly at right angles to the spine. The whole pelvis is shallow, with the ischio-pubic portion placed more backward than in the Elephant. The anterior outlet is large and oval, with the longer diameter antero-posterior. In the fossil variety there is no fork on the anterior superior iliac spine, and the obturator fora mina are more elongated.
In the Hippopotamus thesacrum is very broad and flat from side to side, though arched con siderably longitudinally ; with a considerable angle, and articulated with last lumbar trans verse processes. The iliac wings are almost plane with it, forming a lunzbo-iliac angle of about 150°, and are less expanded, smaller, and more slightly convex, with the two su perior spines directed much dorsally, espe cially the posterior. The ischia are long and comparatively slender, emd directed dorsally, forming a large angle with the ilia, and sup porting large and massy tuberosities, which are parallel to each other, and project by a prominent tubercle dorsally above the coccy geal vertebrm, a peculiarity which causes this pelvis to look altogether like that of the Ox. The pubes are elongated, and the ischio-pubic symphysis also long. The obturator foramen
is large, and the plane of the acetabulum looks downwards and outwards, and is placed at an angle of about 50° from the perpen dicular, being 20° less than that of the Ele phant. The whole pelvis has an open, light, oblique, and flat appearance, with the ischio pubic portion placed more backwards than either the Elephant or Rhinoceros.
In the Hog the sacrunz is narrow, the ilia and ischia rnore elongated, and the latter closer to each other, with prominent and parallel tuberosities. The whole pelvis is elongated and approaches the Carnivore type, as is particu larly seen in the ilio-pubic angle (120'). The lumbo-iliac angle is about 145°.
In the Tapir are three sacral vertebrm, the two upper articulating with ilia, and forming a sacrum arched considerably, both transversely and longitudinally, and with an imperceptible angle. The ilia are remarkab!e for theirlong and somewhat rounded shafts, and the sudden ex pansion of the wings on each side, so as to form a T shape, of which the branches are directed obliquely antero-posteriorly, the posterior branch being articulated to the sacrum, into which they bite well. The crest is thus made slightly concave instead of convex. The sacro iliac facet, which in most marnmalia is lunated in shape, with the convexity directed to the acetabulum, and the concavity to the spinal column, is in the Tapir of a peculiar shape, narrowing suddenly between the two sacral vertebra, and then again expanding, forming two distinct sacral " joggles." The ischia are long, with tubers projecting dorsally ; pubes directed inwards. The lumbo -iliac angle is comparatively very acute (125°) ; the ilio pubic large (145°) ; and the ilio-ischial well pronounced (140'). The whole pelvis is very like that of the Horse, but is distinguished by the greater breadth and curves of sacrum, and by more rnassy proportions, and more distinct T-shaped, and greater expansion of the ilia. The pelvis of the fossil Paleotheziunz has some resemblance to that of the Tapir, but the ilia are longer and more prismatic, and the ischial tuberosities less developed. That of the Anoplotherium is a link between the Tapir and Carael.