118 MAMMALIA. 
elongated body; their very movable spine, which is provided 
with muscles that strongly flex it; their narrow pelvis; their 
short hair, that adheres closely to the skin, all unite to render 
them good swimmers; and all the details of their anatomy con- 
firm these first indicia. 
We have as yet distinguished two genera only, Phoca and 
Trichechus. 
Puoca, Lin. 
Seals have six or four incisors above, four or two below, pointed 
canini and grinders to the number of twenty, twenty-two, or twenty- 
four, all trenchant orconical, and without any tuberculous part what- 
ever ; five toes to all the feet, the anterior ones regularly decreasing in 
length from the thumb to the little toe, while in the hinder feet the 
thumb and the little toe are the longest, and the intermediate ones 
the shortest. The fore feet are enveloped in the skin of the body as 
far“as the tarsus, the hinder ones almost to the heel. Between the 
latter is ashort tail. The head ofa Seal bears a resemblance to that 
of a Dog, whose intelligence and soft expressive look it also pos- 
sesses. It is easily tamed, and soon becomes attached to its keeper, 
or those who feed it. The tongue is smooth, and sloped at the end, 
the stomach simple, cecum short, and the intestinal canallong, and 
tolerably regular. These animals live on fish; always eat in the 
water, and close their nostrils when they dive by a kind of 
valve. As they remain a long time under water, it was supposed 
that the foramen ovale remained open, as in the human fcetus—but 
it is not so: there is, however, a large venous sinus in the liver, 
which must assist them in diving by rendering respiration less ne- 
cessary to the motion of the blood. Their blood is very abundant 
and very black. 
Puoca, properly so called, or without external ears. 
The true Phoce have pointed incisors; all the toes enjoy a certain 
degree of motion, and are terminated by pointed nails planted on the 
edge of the membrane, which unites them. 
They are subdivided, from the number of their incisors. The 
Catocrpnata, Fr. Cuv. have six above and four below; such is the 
Phoca vitulina, L.; Buff. XII, xlv, and Supp. VI, xlvi; PA. 
littorea, Thienem. pl. vi. (The Common Seal.) From three 
to five feet in length; of a yellowish grey, more or less shaded 
and spotted with brown, according to its age; sometimes 
brownish, with small yellow spots. When very old it becomes 
whitish. Common on the coast of Europe in great herds. It 
is also found far to the north ; we are even assured that it is this 
