168 



PELVIS. 



tapering gradually to the posterior extremity 

 of the sacrum, where it terminates in an 

 outward curve ; and placed upon the transverse 

 processes, which it encases, like a frame, 

 on each side, and to which it is firmly anky- 

 losed by its inner surface. In the Ostrich, its 

 thick upper surface or border does not unite 

 with the similar bone of the opposite side, nor 

 with the sacral crest; but is separated from 

 it by a chink," or oval opening, d, gradually 

 narrowing posteriorly, in which the sacral 

 spines (a) are seen distinct and separate, and 

 coalesced only at their extremities. Opposite 

 the three last sacral spines, however, the 

 ilio-sacral pieces are ankylosed to the sacral 

 ridge, and terminate posteriorly the oval chink. 

 In the Emu and Rhea, the ilio-sacral pieces 

 are coalesced in their whole length with 

 the extremities of the sacral spines, and a 

 narrow diamond-shaped dorsal plate is formed, 

 composed almost entirely of the united ilio- 

 sacral plates, and having its angles at the 

 massy ischio-sacral buttresses. 



The ischia (e) are very long and thick, and 

 form, by the superior vertical bifurcation of 

 the cotyloid extremity, a very strong ischio- 

 sacral buttress (/), coalescing at that point 

 with the ilium, sacrum, and ilio-sacral plate. 

 In the Ostrich and Emu the ischia are not 

 connected posteriorly with the sacrum, but a 

 wide and elongated sacro-sciatic notch inter- 

 venes. In the latter, the ischial extremities 

 are free and tubercular. In the Rhea they are 

 ankylosed, by their posterior four-fifths, not 

 only to the sacrum, but, like the ischia of 

 the Bats, to each other, passing in front of the 

 coccyx and greater part of the sacrum, thus 

 excluding them from the pelvic cavity, and 

 enclosing complete sacro-sciatic foramina, which 

 open into a sort of posterior pelvic cavity. 



The -pules (g) are long and slender, and 

 are united posteriorly to the ischia in the 

 Ostrich and Rhea, completing the Obturator 

 Foramina ; but, in the Cassowary, the pubes, 

 as well as the ischia, are free at their posterior 

 extremities, and the obturator foramina are 

 incomplete, like the sacro-sciatic. In the Rhea 

 and Cassowary they are widely diverging ; 

 but in the ostrich they approach each other 

 in a wide curve posteriorly, and unite in a 

 median interpulic symphysis (//), which curves 

 forward anteriorly in a hook-like process, 

 and completes an oblong anterior pelvic outlet 

 with its longest diameter antero-posterior. 

 The ilio-pubic angle is 140 in the Rhea, and 

 155 in the Ostrich and Cassowary. The ilio- 

 pectineal spines are well marked, especially in 

 the Ostrich (m). The acetabula (i) are per- 

 forated, and open partly into the pelvic cavity, 

 and partly upon the sacrum, and are so closely 

 approximated that the bodies of the vertebrae 

 only intervene. Immediately below the ace- 

 tabula, the ischia and pubes are connected, on 

 each side, by the suture of an ischial apophysis 

 with the pubes (&), across the obturator mem- 

 brane, enclosing a smaller obturator opening 

 (/), which transmits the vessels and nerves, 

 and intervenes between the larger obturator 

 opening (o) and the acetabulum. 



In the Apteryx the ilia are longer and more 

 concave superiorly, and the ilio-sacral prolon- 

 gation short ; and both are separated more 

 distinctly from the opposite ones by the 

 coalesced extremities of the sacral spines, 

 forming an elongated ridge of bone down the 

 middle, and separated from the ilia and ilio- 

 sacral pieces by distinct parallel sutures. 



The ischia, in this bird, as well as in the 

 fossil gigantic Dinornis, or wingless bird of New 

 Holland, are not placed, as in the Cursores 

 before mentioned, parallel with the ilia, but 

 form an anteriorly retiring or reversed ilio- 

 ischial angle of 140 ; and they do not coalesce 

 posteriorly, either with the pubes or the 

 sacrum, but have free truncated extremities, 

 presenting a great general resemblance to 

 the pelvis of the Emu. The pubes are parallel 

 to the ischia, and, like them, free and diver- 

 gent. 



In the Natatores the pelvis is long and broad, 

 and generally much expanded posteriorly by 

 the divergence of the ischia and large sacro- 

 sciatic ossification, for the attachment of the 

 powerful muscles used in swimming ; and the 

 great intercotyloid distance gives to their gait 

 its peculiar waddle (see fig. 104.). That of 

 the Loons and Penguins, however, is remark- 

 ably contracted, long, and narrow, with little 

 intercotyloid distance. 



The usual number of sacral vertebrae is 

 fourteen, as in the Swan ; the Grebe has 

 thirteen, and the Duck fifteen, and the sea 

 Swallow ten only. The sacrum is usually 

 very broad ; but in the Penguin and Loon it is 

 unusually narrow, and in the former it is united 

 by ankylosis to the last dorsal vertebra. The 

 coccyx is usually composed of eight pieces. 

 The Goose and Pelican have but seven, and 

 the Barnacle Goose nine. In Penguins it is 

 strong, and assists in the support of the body 

 in its usual vertical position. It is usually 

 curved much dorsally, affording a larger pos- 

 terior pelvic outlet. 



The ilia are moderately long, and overlap 

 the posterior ribs. In the Penguin they are 

 said, by Wagner, not to be ankylosed to the 

 sacrum, but connected only by ligamentous 

 union ; thus increasing its loose and waddling 

 gait. The ischia are very long, divergent, and 

 largely expanded into a very broad sacro- 

 sciatic element, enclosing a small sacro-sciatic 

 foramen. They are prolonged posteriorly into 

 a sort of styliform process in the Auk and 

 Puffin. The pubes are very long, slender, and 

 divergent, and are expanded at the extremity, 

 and curved inwards in the Swan, Diver, arid 

 Gannett. They do not generally unite with 

 the isrhia posteriorly ; but, in the Swan, Duck, 

 and Pelican, the obturator foramina are com- 

 pleted by the union of these bones, and are 

 small and elongated. 



The GallinccE have large and strong pelves, 

 in correspondence with their powerful legs, 

 used chiefly for progression and scratching up 

 their food. 



The sacrum is broad, and composed of 

 from ten pieces, as in the Turkey, to fifteen 

 in the Pheasant and common Fowl. The 



