a3 STRENTA 
very existence would have been unknown to science but for the 
interesting account of its anatomy and habits left by Steller, and 
the few more or less imperfect skeletons which have recently re- 
warded the researches carried on in the frozen soil of the islands 
around which it dwelt. There is no evidence at present of its 
having inhabited any other coasts than those of the islands just 
named, although it can hardly be supposed that its range was 
always so restricted. When first discovered it was extremely 
numerous in the shallow bays round Behring Island, finding 
abundant nutriment in the large laminarie growing in the sea. 
Its extirpation is entirely due to the Russian hunters and traders 
who followed upon the track of the explorers, and, upon Steller’s 
suggestion, lived upon the flesh of the great Sea-cows. Its 
restricted distribution, large size, inactive habits, fearlessness of 
man, and even its affectionate disposition towards its own kind 
when wounded or in distress, all contributed to accelerate its final 
extinction. 
According to Steller’s account, the Rhytina had a skin of a dark 
brown colour, sometimes spotted or streaked with white. The fore 
limb was covered with short brush-like hairs. 
EXTINCT SIRENLANS. 
Halitherium.—The Miocene and early Pliocene seas of Europe 
abounded in Sirenians, to which the generic name of Halitherium 
was given by Kaup, but which have also received other names. 
They had large tusk-like incisors in the upper jaw, as in the 
existing Dugongs, though not so greatly developed. Their molar 
teeth were 3 or $, anteriorly simple and single-rooted, posteriorly 
those above with three and those below with two roots, and with 
enamelled and tuberculated or ridged crowns, in all which respects 
they more resemble those of the Manatee than of the Dugong. 
The anterior molars were deciduous ; and there is evidence of the 
presence of milk-teeth. Germs of inferior incisors were also 
present. Some species at least had nasal bones, short, broad, 
but normal in position, whereas in all the existing genera these 
bones are quite rudimentary. Another and still more important 
evidence of conformity to the general mammalian type is the 
better development of the pelvic bone, and the presence of a small 
styliform femur articulated to the acetabulum, although no traces 
of any other part of the limb have been discovered. These ancient 
Sirenians, which may be regarded as representing a distinct family 
—Halitheriide—were thus, in dental, cranial, and other osteological 
characters, less specialised than are either of the existing species, 
1 Kaup, Veues Jahrbuch, 1838, pp. $19 and 536. 
