7io 



MAMMALIA. 



depths on the floor of the ocean, and is often preserved as 

 a fossil. 



There are at least rudiments of two sets of teeth, as 

 in other Mammals, but in baleen whales only the teeth of 

 the milk set are calcined, and they come withal to nothing, 

 being to some extent replaced by the 

 horny baleen-plates developed on the 

 palate. In toothed whales the two sets 

 are said by Kiikenthal to fuse, but the 

 usual interpretation is that the func- 

 tional teeth belong to the milk set. It 

 is possible that the simple, homodont, 

 conical teeth of Odontoceti have resulted 

 from a splitting of more complex cusped 

 teeth. No clavicles are developed. 

 The bones of the fore-limb are flat- 

 tened, and, except at the shoulder, 

 articular surfaces are not developed, so 

 that the limbs form stiff paddles. The 

 carpals are fixed in a fibrous matrix, 

 tend to be rudimentary, and are often 

 unossified. They cannot be readily 

 compared with the members of the 

 typical mammalian carpus. In the 

 absence of true joints, a slight flexibility 

 is given by the absence of ossification. 

 There are four or five nailless digits, of 

 which the second and third, and some- 

 times the first, may have more than the 

 usual number of phalanges, (see Fig. 

 314), a peculiarity possibly due to a 

 duplication and separation of epi- 

 physes. The pelvis may exhibit a 

 rudimentary ischium, with small vestiges of femur and 

 tibia. 



The rounded brain is relatively large, with well-convoluted 

 cerebral hemispheres. 



As to the alimentary system, — salivary glands are rudi- 

 mentary or absent, the stomach is chambered, the intestine 

 has rarely a caecum, the liver is but slightly lobed, there is 

 no gall-bladder. 



Fig. 314. — Fore-limb 

 of whale [Megaptera 

 longimana). — After 

 Struthers. 



