VERTEBRATA. 35 



manner of connection of the bones entering into the formation of 

 this cavity. The chimpanse and elephant afford ns the nearest 

 approach to the human formation, even here the ilia are narrow 

 and elongated ; and the sacrum and coccyx are flat, contracted, and 

 continued in a direct line with the spine. Next in the order of 

 development may be ranked the rhinoceros, the ox, the horse, the 

 carnivora and the rodentia. In ant-eaters, moles, and shrews, the 

 symphysis pubis remains open; and in the two latter genera the 

 pelvis is so small that the pelvic viscera are placed without it. The 

 megatherium and sloth, however, have pelvis of large dimensions. 

 Some of the edentata, as the dasypus, have the ilia joined to the 

 sacrum. In others, as the sloth and some of the ant-eaters, the 

 ischium is connected with the sacrum, forming an ischiatic foramen, 

 instead of a notch. The cetacea present but slight rudiments of a 

 pelvis in the form of two small bones united to each other and to 

 one of the vertebrae by cartilage. Finally the marsupial animals 

 present a small, elongated pelvis, especially remarkable for the pre- 

 sence of two particular bones not found in any other mammiferous 

 animal even in a rudimental state, and named 0.95a marcip'ialia. 

 These bones are attached, but not articulated, to the anterior part 

 of the pubis, near the symphysis; each is about three inches long 

 in the kangaroo, flat, with anterior thin, and a posterior thick 

 edge. The bone is triangular in form, the broad end being at the 

 pubis, while the narrow has attached to it the abdominal muscles. 

 The use of these bones is to support the marsupium, or abdo- 

 minal pouch, in which the mammary apparatus is lodged, and the 

 young animal nurtured. 



The posterior or abdominal extremity is altogether absent in 

 the cetacea. In the other mammalia inhabiting the sea, the seal, 

 for instance, the several elements of the posterior extremity, even 

 the toe-nails, are distinctly recognisable, but consolidated by a 

 membranous web into a kind of caudal fin. 



The femur in the lower mammalia is short and straight ; the 

 neck is either absent or but little developed, the head being placed 

 vertically over the shaft. The trochanters and linea aspera are 

 badly marked. This bone is shorter than the tibia, the converse to 

 what obtains in man. In the megatherium its thickness equals 

 half its length. The trochlea is a deeper and the transverse 

 diameter of the condyles less than in man. 



The patella is usually present in the mammalia; best developed 

 in the pachyderms, solipeds, and monotrems; least so in the carni- 

 vora and quadrumana; and wholly absent in the marsupiata and 

 cheiroptera. 



Tibia and Fibula. — Throughout the mammalia these bones 

 coincide pretty nearly with those of the fore-arm. As in man, the 

 tibia forms the chief bone of the leg. The fibula is analogous to 

 the ulna, and is found only in a rudimentary state in the solipeds 

 and ruminants, as the latter bone was in these animals. In the 

 solipeds, the fibula is applied to nearly the upper half of the outer 

 surface of the tibia, being pretty large above, and ending in a fine 



