Order III. Sirenia. Sirenians. 
The Sirenians are mammals constituted especially for an aquatic 
life, and formerly were confounded with the Cetaceans, with which, 
however, they have no relationship. Like the members of the Order 
CeracEa, the Sirenians have no hind limbs, and those on the forward 
part of the body have been transformed into paddles, and the tail 
has been expanded into a flattened rudder. 
The head is of the ordinary mammal type, being small for the 
body, with a rounded superior outline, but the nostrils are provided 
with flaps that open and close at the will of the animal. There are 
no fins. The eye is small, and the ear has no external conch. Thick 
lips, provided with a number of bristly hairs, cover the small mouth, 
and the skin of the body is thick, with sometimes hair distributed 
sparsely over it. The female has two pectoral mamme. ‘Teeth are 
entirely absent in some species, like Steller’s Sea-Cow, but others 
have both incisors and molars. The bones of the skeleton are 
massive and dense, the skull being remarkable in this respect. Collar 
and nasal bones are absent and there is no sacrum, but the pelvis 
is represented by a pair of small bones. The two bones of the fore- 
arm are usually ankylosed at the extremities, and the digits are five 
in number. The lungs extend backward nearly to the last rib and 
are very narrow. Rough, horny plates cover the symphysis of the 
mandible, and the surface of the tongue is similar to these plates. 
Three species of Manatee are included in the family, one of which, 
Steller’s Sea-Cow (Hydrodamalis gigas), is now extinct. This animal, 
the largest of all, was from twenty to twenty-eight feet in length, 
and at the time when Steller visited Bering Sea in 1741, was very 
numerous around Bering and Copper Islands. The flesh, unfortu- 
nately, was found to be highly palatable, far superior to salt pork, 
and the sailors slaughtered the inoffensive beasts, until the last one 
was killed in 1768. No skin has been preserved, and a collection of 
bones in St. Petersburg and Washington alone remain to show what 
kind of animal it was. Two living species of Manatee remain in the 
New World, one, 7. manatus, in southern North America; the 
other, 7. inunguts, restricted to the rivers Amazon and Orinoco, in 
South America. In the Old World, one, 7. senegalensis, is confined 
to West Africa in the district comprised between 10°—16° latitude, 
and 20°—27° longitude. East Africa, Australia, Ceylon, and islands in 
the Bay of Bengal, the Indo-Malay Archipelago and the Philippines 
possess the Dugong, more a marine animal than the Manatee, which 
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