16 MAMMALIA. 



and united to 7 or 8 sacral vertebrae. In the Apes with tuberosities, 

 the ischia are broad and flat inferiorly, as if cut off. The spine of 

 the ischium occurs only in the Apes. On the other hand, in some 

 Cheiroptera and Edentata, the spines of the ischia coalesce posteri- 

 orly, or with the sacral and caudal bones, so that the sciatic notch 

 is always converted into a true foramen. The foramen ovale is 

 often very large, and occasionally, as in Phoca, the two bones en- 

 closing it are very much elongated. The acetabulum has almost 

 always a bottom, and frequently a depression for the insertion of the 

 ligamentum teres, which latter is, however, completely wanting even 

 in the higher Apes. The acetabulum is very seldom perforated, as 

 in Echidna (and in all Birds). In the Ai, which has such an un- 

 seemly gait, the acetabulum is very small and shallow. From the 

 anterior or upper border of the pubic bones there frequently arises 

 a pointed spine-shaped eminence (eminantia ilio-pectinea), which is 

 the first indication of a marsupial bone, e. g. in Vespertilio spec- 

 trum. In the Monotremata and Marsupiata there is constantly 

 placed in the same situation the marsupial bone, an elongated cylin- 

 drical and triangular bone, the free point of which is directed for- 

 ward. It may be regarded as formed by a partial ossification of 

 the fibres of the external sheath of the abdominal muscles. The 

 pelvic bones are very simple in the Cetacea, and appear sometimes 

 to be entirely wanting, as in Manatus. In the Dolphins they con- 

 sist of two simple elongated bones lying near the anal and genera- 

 tive organs, which converge together from opposite sides, or else, as 

 in many Whales, are connected by a transverse piece, this rudi- 

 mentary form of pelvis frequently resembling the hyoid bone of Man ; 

 in the Dugong a small Y-shaped bone is the representative of the 

 pelvis. 



The Posterior Extremities exhibit a great general resemblance to 

 the anterior. The femur preserves the human type in the different 

 orders more than the humerus. The trochanter major is often very 

 large, and extends beyond the head of the bone ; the internal tro- 

 chanter is occasionally wanting, and in a number of animals, e. g. 

 Castor, Dasypus, Equus, but in the Rhinoceros especially, we meet 

 besides with a strong process more or less in the middle, resembling 

 a third trochanter. In the Cheiroptera the head of the straight 

 femur lies in a peculiar manner between the two trochanters, which 

 are of equal height. The femur is short in the Solipedia and Ru- 

 minantia, and particularly so in the Seals. In the leg, the tibia is 

 always the principal bone and the main support of the femur. The 



