The innominate bones are very large. The iliac wings are much spread out, widely con cave anteriorly, and slightly convex posteriorly, these surfaces being directed forwards and' backwards. The iliac crest presents a con tinuous, well-arched curve, and at the inner part of its centre (m) it is prolonged and curved forward in a lip which overhangs the anterior fossa, and contributes to support the bulky viscera. The lips of the crest are remarkably spread. The posterior superior spine is continued by an oblique crest of bone (a) to the lateral tubercles of the lower sacral vertebrm, as if from ossification of the oblique sacro-iliac ligament. The posterior inferior spines are continued by a ritlge to the borders of the fifth, sixth, and seventh sacral pieces into the bony ankylosis of these with the ischia, which are ankylosed to the same parts, evidently in the position of the sacro sciatic ligaments (d). The ischia (c) are comparatively short and directed obliquely backwards and downwards, and have remark ably slender tuberosities, as is the-general cha racteristic of the Sloths. The inferior rami (k) slope much forwards, and join with the pubis in a plate of bone (h) before reaching the symphysis (f), which is very narrow and formed by the pubes only. The pubes (b) of the Mylodon are long and very slender, and form an angle of about 160° with the ilia, the apex of the angle being directed forwards, a remarkable peculiarity, by which it differs, in common with the Ant-eaters, from the other Mammalia. The vertebro-iliac angle is rather acute, being about 125°, and the dio-ischia/ is as small as 120°, being very near the human angle.
The whole pelvis is remarkable for its breadth and shallowness. The anterior outlet is of an oval form, with the long diameters antero-posterior. The posterior opening is somewhat pentagonal, and, from the great antero-posterior direction of the ischial rami and the ossified sacro-sciatic junction, pre sents a flat level rim. The sacro-sciatic fora men (0 is comparatively small, but the obtu rator foramen (o) is large and oval.
The pelvis is one of the most characteristic parts of the fossil Megatherium, as forming the fulcrum of muscular forces of unusual N igou r. The sacrum is very narrow, and shorter proportionably than in the My-lodon, and is composed of five vertebra, only the last being broader transversely. There is no ankylosis to the last lumbar vertebra.
The iliac wings are large and expanded, with a concavity directed forwards, the ante rior superior spines overhanging the femurs, and the -external border very concave. They are more massy than in the Mylodon, and present no hook-like process on the crest. The ischia are broad, blade-like, and massy ; the tuberosities are not well marked, but rounded and ankylosed to the lower sacral vertebra, enclosing a small foramen, and contributing, with the ankylosed ilia, to sup port the weight of the animal. llio-ischial angle 125°. The pubes are slender and very oblique, and form, like the Mylodon, a reversed ilio-pubic angle of about 155°. The pubic
symphysis is narrow, and presents anteriorly a rostrated projection. The acetabula are large and near to each other ; the planes are inclined from the perpendicular about 65°. The anterior outlet is oval, with long diameter antero-posterior. The posterior has the long diameter transverse. The obturator opening is comparatively- small. The whole pelvis has a very massive appearance.
The pelvis of the other Edentata presents the same general type as that of the Sloths. In the Armadillo (Dasypus longicaudus) there is a sacrum of nine vertebra, the three upper of which are ankylosed to the ilia, and the sacral spines are coalesced in a crest. The sacrum is narrowed to a remarkable extent between its iliac and its sciatic portions, ex panding rnuch in the latter part to meet and coalesce with the ischia, with which it forms a broad osseous plate in the site of the sacro sciatic ligaments. The oblique sacro-iliac ridge is also well marked. The caudal bones are numerous.
The ilia are long, strong, broad, and pris matic, and the ala are prolonged into broad lamellar plates, which are ankylosed con tinously to the sacrum, and assist to support the carapace. The ilia are much more ap proximated to each other than the ischia. Lumbo-iliac angle 155°. The ischia are large, broad, and considerably divergent, with broad tuberosities prolonged dorsally to support the shell ; coalescing in a broad plate with the lower sacral pieces, and enclosing a moderately sized sacro-sciatic foramen. The rami are at right angles to the body of the ischia. The ilio-ischial angle is marked, (145°). The pubes are slender and very obliquely directed back wards, making an itio-pubic angle of 150'; and the symphysis is short, especially in the Weasel-headed Armadillo, in which also the ilio-pubic angle is smaller. (I30°). The pos terior pelvic outlet is much larger than the anterior, from the greater eversion of the ischia. In the Cape Ant-eater (fig. 102.) the SaC77.1111 is composed of six pieces, with the spines (a) coalesced, but leaving foramina between them, and the last transverse processes (b) elongated. Caudal bones numerous (fig. 102.).
The ilia are very thick and prismatic, and more perpendicular to the spine, with the an terior and posterior borders thickened into a strong ridge. The ala are concave externally, the posterior superior spines (e) prolonged dorsally, and ankylosed to the sacrum, and the anterior superior (g), prolonged and curved outwards and downwards. The ischia are very long, expanding into a broad plate poste riorly (c), but do not touch the last sacral vertebra. The ischial spines (i) are marked, and the tuberosities present two tubercular projections, one directed outwards, long and sharp (k); and the other thicker, and directed dorsally (/). The pubes (d) are directed obliquely backwards with very short sym phy sis ( f), and the ilio- pectineal spine (h) is very large. The pelvis is altogether massy and large, with long sciatic notches and con siderable obturator foramina.