PELVIS. 



165 



ankylosed at the tuberosities with the last 

 sacral vertebrae, and, as seen especially in the 

 Ternate Bat, given in the above figure, pre- 

 senting an appearance as if ankylosed to each 

 other in one mass, from the extreme narrow- 

 ness of the sacrum tit that part, inclosing a 

 small sacro-scialic foramen. The pubcs (b) 

 are thick, short, and very oblique, joining with 

 the short ischial rami at d, to form an elon- 

 gated obturator foramen (/). The ilio-pectineal 

 spine (/*) is very prominent, and recurved 

 almost like a marsupial bone. This is especially 

 seen in the Vespertilio spectrum, in which it is 

 considered by Wagner as the first indication of 

 a marsupial bone. The pubic symphysis is 

 totally wanting generally in the Bat tribe, 

 leaving a large interval (d, d') ; but, accord- 

 ing to Pallas and Schreger, the males of some 

 species possess a symphysis, which is wanting 

 in the female, a peculiarity curiously illustra- 

 tive of the influence of sex on the pelvis. In 

 a specimen in the Hunterian Museum the 

 symphysis, or a close approximation of the 

 bones, is certainly present, though very short. 

 The cotyloid cavities in the bats are closely 

 approximated, and are directed backwards as 

 well as outwards, causing the retroversion of 

 the feet seen in these animals. The pelvic 

 cavity and outlets are much more capacious 

 than in the Mole and Shrew. 



In the Ceiacea, which are in other respects 

 osteologically allied to the Packydermata, the 

 pelvic development suddenly becomes dege- 

 nerated into small elongated bones, which 

 may be considered as the homologue of the 

 pubes, and which are imbedded in the muscles 

 of the abdomen immediately in front of the 

 ventral opening, and give attachment to the 

 crnra penis. They differ, only in being thicker 

 and less transparent, from the pelvic bones 

 of the true Fishes, between which and the 

 Mammalia these animals are the connecting 

 link, as the Bats to the Birds, and the Mo- 

 notremata to the Chelonian reptiles. 



In the Dolphins these pubic bones are two 

 simple, elongated, flat bones placed on each side 

 of the median line. In some Whales they are 

 connected by a cross piece, and assume a 

 hyoid shape (sec fg. 257. Art. Cetacea). In 

 the Dugong it is a V-shaped bone formed of 

 four pieces, and articulated to one of the ver- 

 tebras by its free extremities. In the Manatiis, 

 according to Cams, they are entirely wanting. 



The pelvic structure of Birds is charac- 

 terised by very evident distinctions from the 

 mammalian type, the osseous parts being ac- 

 cumulated, as it were, on the posterior and 

 lateral parts, leaving the anterior parietes 

 deficient, and being also thinner and more 

 spread out, so as to leave smaller foramina. 



The sacrum (fig. 104. ) is generally broad 

 and large, consisting of from eight to twenty 

 pieces, being increased forwards by ankylosis to 

 the vertebras corresponding to the lumbar 

 region of the Mammalia, and which contribute 

 to support the iliac wings. This arrangement, 

 as well as the extensive ankylosis of the ilia 

 and ischia, has an evident relation to their 

 bipedal support, and is compensatory for the 



deficiency of the pelvic circle anteriorly. It 

 is much more extensive in the Cursores and 

 those which use the legs as the most usual 

 instruments of progression. The bodies of 

 the sacral vertebrae are raised in a continuous 

 ridge on the anterior aspect, those imme- 

 diately between the acetabula being larger 

 and broader than the rest (fg. 105. a). The 

 first five or six (.1'), which may be considered as 

 the ankylosed lumbar vertebra?, present marked 

 spinous processes united in a high crest which 

 intervenes between, coalesces with, and sup- 

 ports the iliac wings at their inner margins 

 (fig. 104-. 6). Their transverse processes, 

 which are also ankylosed to the ilia near their 

 outer borders, are strong and well marked on 

 the ventral surface, and differ from those of 

 the true sacral vertebrae in being more pro- 

 minently advanced and having a direction 

 more horizontally outwards instead of back- 

 wards and upwards {fig. 105. r), the most pos- 

 terior being the thickest and placed at the 

 junction of the iliac wing with the shaft. A 



Fig. 104. 



Superior or dorsal aspect of the pelvis of the 

 Duck : a, sacrum ; b, coalesced lumbar spines ; c, 

 sacral suture; d," ilium; e, cotylo-saeral rib; f, 

 ischio-sacral buttress ; g, sacro-iliac plate ; It, sacro- 

 sciatic plate; i, acetabulum; /.', ischium ; /, sacro- 

 sciatic foramen ; m, rudiments of ischial ramus ; n, 

 spine; o, anterior obturator,, foramen ; ;>, pubis; q, 

 ilio-pectineal spine ; r, anterior ischio-pubic union. 



little anterior to the acetabula, however, 

 where the true sacral vertebrae may be con- 

 sidered to commence, the spines gradually 

 become less marked as they emerge from 

 between the iliac wings and form a more or 

 less flattened surface (a), which is separated 



M 3 



