160 



PELVIS. 



the latter pelvic type, which approaches in 

 general form to the pelvis of the Jerboa, just 

 considered. 



The sacrum of the Wombat is very flat, and 

 strong, and broad, in correspondence with 

 the general squat and massy skeleton of the 

 animal (see figs. 102. and 108. Art. Marsu- 

 pialia). Its curve is a continuation of that 

 of the dorsal and lumbar vertebra?. The 

 number of sacral vertebrae is seven, and the 

 transverse processes are separated from 

 each other, the three upper of which are long 

 and strong, and are articulated by their tips to 

 the ilia. The facet on the extremity of the 

 first looks upward and outward, and that on 

 the second, on the contrary, downward and 

 outward, and form projections which impinge 

 upon the iliac facet. This arrangement in the 

 Wombat like that in the Tapir, is closely ana- 

 logous to the formation of the sacral "joggles," 

 and the alteration of the inclination of the 

 sacral wedge in Man, at the point of the auri- 

 cular surface opposite the second sacral piece, 

 substituting for upward, backwards, and for 

 downward, forwards, a change consequent on 

 the difference between the prone and erect 

 positions. Caudal pieces are numerous. 



The ilia are comparatively short and ex- 

 panded considerably, and are curved out- 

 wards in a remarkably strong, broad, hook- 

 like process at the anterior superior spine. 

 They are placed very obliquely on the spine, 

 being at an angle of 160 with the lumbar 

 portion of the great dorsal curvature. The 

 ischia are thick, long, and massy, and in a 

 right line with the ilia. They have cu- 

 riously bifurcated tuberosities, one tubercular 

 projection turning inward, and the other 

 longer, curving outward, in another remark- 

 able and strong hook-like process, to which 

 formation we have before remarked a tendency 

 in the Hare and other Rodents (Jig. 98. e). 

 These processes, like those on the ilia, afford 

 a powerful hold and leverage to the strong 

 muscles of the hinder extremities, much used 

 by the animal in its burrowing habits. These 

 hook-like processes of the ischia are formed 

 by a Y-shaped apophysis analogous to that of 

 tne tuberosity in man. The pubes are short 

 and thick ; and the symphysis is parallel to 

 the spine, very long, and joined in very ex- 

 tensively by the vertically directed rami of the 

 ischia. 



The marsupial bones of the Wombat are long, 

 flat, rounded and expanded at their free extre- 

 mities, and articulated to the anterior border of 

 the pubes in the position of the crests by two 

 articular facets separated by an arched interval. 

 Ilio-pectineal spines are present, and of large 

 size. 



The whole pelvis of the Wombat is large and 

 massy, though the openings and outlets are 

 proportionably very small. It has a flattened 

 appearance antero-posteriorly, so that the 

 anterior outlet has its greatest diameter trans- 

 versely placed. 



In the Myrmecobius fasciatus this flattened 

 appearance of the pelvis is still more remark- 

 able. 



In the Opossums, Pcramcles, and Pha- 

 langers, there is but one sacral vertebra, which, 

 in the Phalangista Cookii y is ankylosed to the 

 last lumbar vertebra. 



The pelvis of the Thylacinus Cynocephalus 

 approaches closely in many respects to the 

 type of the Carnivora, like many of the 

 peculiarities of this animal. The sacrum pre- 

 sents no angle ; the ilia are massy, somewhat 

 short, and less oblique than those of the 

 Wombat ; the ischia are also short and thick, 

 and are placed at an open angle (170) with 

 the ilia, while the pubes are short and di- 

 rected almost horizontally inwards, making 

 an antero-posterior angle with the ilia as little 

 as 115. The whole appearance of the pelvis 

 is massy, with small openings. It has neither 

 the oblique appearance and exaggerated pro- 

 cesses of the Wombat, nor the elongation and 

 wide outlets of the Kangaroo, while its well- 

 marked ilio-pubic angle contrasts much with 

 both, and shows a strong similarity to the 

 Carnivora. 



In the Kangaroos, the sacrum is in the line 

 of the lumbar curve, and differs in little but 

 size and breadth from the preceding vertebrae. 

 There are twt> sacral vertebra?, articulating 

 with the ilia, their transverse processes being 

 long and coalesced, but the spinous processes 

 distinct. In the Potoroo there is one only, 

 with large lateral processes. The caudal 

 vertebrae are numerous and very strong, and 

 their upper normal spines encroach much on 

 the diameter of the pelvic cavity and posterior 

 outlet. The ilia have short, strong, and pris- 

 matic shafts as in the Rodents, with alae of the 

 same shape, much elongated and turned out- 

 wards, though in a much less degree than in the 

 Wombat, and terminating in narrow clubbed 

 crests (jig. 99. g). There is a rudimentary 

 inferior anterior spine (/*). The upper part of 

 the iliac wing projects much on the dorsal 

 aspect of the spinal column, forming with it 

 an angle of 140 (see fig. 112. 9.). The ischia 

 are very long, broad, and strong, and have 

 much-expanded tuberosities with an outward 

 curvature (fig. 99. e). These are united in a 

 median symphysis by a single V-shaped epi- 

 physis (c), divided, in the adult, by a suture 

 from the ischia. The tuberosities support also 

 another epiphysis on each side posteriorly at e, 

 the anterior ischial rami being almost deficient. 

 The ilia and ischia are very nearly in a direct 

 line. The pubes are moderately long, slender, 

 and directed much downward, so as to give to 

 the anterior outlet a triangular shape, with the 

 base at the broad sacrum, and the apex at the 

 pubic symphysis. The ilio-pubic angle is 135. 



The marsupial bones (a y b ) are smaller, 

 rounder, and more curved externally than in 

 the Wombat. Their free extremities are tuber- 

 culated and not flattened, and they are articu- 

 lated to the pubic crest near the symphysis by 

 a single facet only, the inner, the position of 

 the outer one being marked by a slight tubercle 

 (6). The ilio-pectineal spines (d) are very 

 large, for the attachment of powerful psoae 

 muscles. 



The direction of the ischio-pubic symphysis 



