126 SKETCH OF THE HISTORY OF MAMMALIA. 



toxodon, pp. 104 and 111, he will find that we have 

 there alluded to the dugong or duyong, and the lamantin 

 (the Aquatic Gravigrades of Blainville), as belonging 

 to the pachydermatous order, and as having in manners 

 and organization little relationship to the true whales, ex- 

 cepting in so far as they are alike modified for the waters 

 of the deep. 



In their external form, indeed, these aquatic pachy- 

 derms are whale-like : there are no hinder limbs, the 

 pelvis being either rudimentary or wanting, and the fore 

 limbs are converted into flippers or paddles ; the body is 

 continued conical till it terminates in a transverse or hori- 

 zontal tail, consisting of an expanse of cartilage covered 

 with tendinous fibres and skin, and which is the chief organ 

 of aquatic locomotion. The skin is almost naked, oily, 

 and covers a layer of subcutaneous blubber or fat ; the lips 

 are studded with thick wiry bristles. Although the nasal 

 opening is placed high on the skull, the nostrils in the 

 skin are placed at the extremity of the muzzle, which is 

 remarkably obtuse and truncate — a form advantageous for 

 the browsing habits of these animals, which feed on sub- 

 marine vegetables. The eyes are protected by a mem- 

 brana nictitans, and the teats in the females are situated 

 just behind the roots of the flippers — two points of 

 difference between these aquatics and the whales. The 

 stomach is sacculated ; the teeth present flat bruising 

 surfaces; there are no intercostal and intra-vertebral 

 arterial plexuses, as in the true Cetacea. (Fig. 83.) 

 The bones of the skeleton are of dense texture and 

 destitute of medullary cavities ; they are not loaded 

 with oil, as in the Cetacea. In the Indian dugong 

 there are seven cervical vertebrge, nineteen costal verte- 

 brae, and thirty lumbar, pelvic, and caudal. In the 

 dugong of the Red Sea the lumbar, pelvic, and caudal 

 vertebras amount to thirty-three ; making in all fifty- 

 nine. The number of the ribs is nineteen on each side. 

 The lower jaw is articulated to the cranium by a true 

 synovial capsule, reflected over cartilaginous surfaces, 

 and not, as in the true Cetacea, by a coarse oily liga- 

 mentous substance. In the lamantin, or manatee, the 



