In the Lemurs, or Makis, the sacrum is in a right line with the spine. Of the three sacral vertebrm, the first only articulates with the ilia, and the last is not ossified to the second. They differ little from the lumbar vertelarm, except in the thicker transverse processes. Caudal vertebrx numerous. The pelvis generally is very weak, narrow, and short. The ilia are narrow and almost pa rallel with the spine, and the ilio-pectineal eminence is unusually well marked ; but the ischial tuberosities are delicate, indicating the less frequent sitting posture in these animals, and a still greater tendency to quadruped pro gression. In the Lemur albifrons, however, the sacrum is broader ; ilia more expanded ; ischial tuberosities larger and more expanded; ilio-pubic angle 120°. In L. tardigradus the sacrum is long, narrow, and keeled in the middle, being ankylosed to the last lumbar and three firat coccygeal vertebrm, as in birds.
The ilia are narrow and cylindrical; pubes long, large, oblique, with no ilio-pectineal apo physis ; iscitia short, with horizontal rand and tuberosities passing backward to articulate with the transverse processes of the upper coccygeal vertebrm, another bird-like arrange ment. In L indri the sacral pieces are four, with comylete ankylosis, the two or three upper articulating with the ilia. Ilia expanded, with extended crest and external fossa, and reaching to the penultiniate lumbar vertebra! ; Ischia very short, with more expanded tubers ; pubes less oblique. In L. volans, or Galeo pithecus, the sacrum has five vertebrw, the first only articulating with ilia. Ilia small and narrow ; ischia with large posterior angle ; pubic symphysis very short. In the sub genus Sterops, the slender Loris presents a remarkably elongated and contracted pelvis. The sacrum is long and narrow, with the two upper pieces articulating with ilia. Ilia slender, long and columnar, and nearly parallel with spinal column ; ischia small, flattened laterally, placed in a line with the ilia, and very near each other, so that the cotyloid cavities are closely approximated ; the lateral diameters very short, and the inferior outlet a mere chink. The pubes are long, projecting forwards, down wards, and inwards, being in clined to each other at an angle of 40°, causing the superior outlet to be trian gular, with the base at the inter-cotyloid diameter, and the apex at the symphysis pubis. This pelvis is also remark able for the extreme angularity of the pubic portion with the iliac, the ilio-pubic angle being 75°, or less than a right angle, the only instance of the kind I have rnet with. (See g. 93. a,b, c.).
Pelvis of the slender Loris, lateral view.
The animals most allied to the preceding order of primates in the form of the pelvis, taken in conjunction with their general struc ture, are the Carnivora. In these, as in most multidigital animals, the pelvis is so con tracted that the trunk resembles an in verted pyramid ; whereas in man, constructed for an erect posture, the base of the pyramid is in the pelvis. Climbing animals, such as
the Apes, Bears, and Sloths, present the nearest approach to the human structure in this particular.
In estimating the sacro- and ilio-vertebral angles in the succeeding orders of Mammalia, it should be observed that, from the coin cidence of the lumbar curve with the great dorsal curvature of the spinal column and the elevation of the neck, the vertebrm cannot be considered as being placed in one general plane, as in man. The line of direction of the lumbar vertebrm has, therefore, been taken for the sacral and iliac angles.
The sacrum, in the Carnivora (a, fig. 94.), is narrow, flat, and triangular, with long and distinct•spinous processes, and placed almost in a right line with the spine. In the Bear, however, from its climbing habits, the sacrum is broader, larger, and more massy, and the sacro-vertebral angle more marked. The number of sacral vertebrm is three in the great majority of the species, the two upper articulating with the ilia ; but in the Ilymna there are but two, in the Tiger four, in the brown Bear five, and in the white Bear as many as seven. The coccygeal or caudal ver tebrx (b) are generally very numerous.
The ilia are moderately long, thick, and narrow in their whole extent, and are placed very obliquely upon the lumbar vertehrm, forming with them an angle of about 150° to 160° ; but in the Bear and Hymna 140° only. The external surface of the elongated iliac wing is concave, and the internal flat and turned inwards towards the spine ; the crest (c) thick, narrow, acutely arched, and pro jecting backwards beyond the spinal column. The ischia are long, strong, prismatic, some what expanded posteriorly, and considerably divergent, but directed in the same antero posterior plane with the ilia, forming toge ther a very long ilio-ischion element. This disappearance of the antero-posterior, ilio ischial angle, which commenced in the Apes, is, in the Carnivora, arrived at its greatest extent, and in the Tiger is even reversed or bent downwards in the opposite direc tion about 15° (see g. 112. 5). With the great obliquity of the ilia, this affords, in the quadruped position, a longer and more power ful leverage for the muscles of the hinder extremities to execute their characteristic bounds, and, like the reverse formation of the ilio-pubic angle, it is another great distinction between these and human pelves. The ischial tuberosities (e) have an outward direction, as well as the ischia generally, and the spine (g) is a mere rudimentary ridge. The pubes are short, and the symphysis (f ) is long, being formed generally both by the ischium and pubis. The ilio-pubic angle varies from 110° in the Tiger, to 120° in the Lion and Leopard, and 125° in the Bear and Hymna.