552 SIRENIA. 



to the breast with their flipper. This fact (if true) together 

 with the pectoral position of the mammae, and the habit they 

 have of raising their head out of the water, may have given 

 origin to the legend of mermaids. 



Numerous remains of Sirenians are known in the Miocene 

 and Pliocene of Europe and N. America. 



Manatua Storr (Trichechiis), manatee ; to 8 feet ; dentition * i f , m \\, 

 the incisors lie beneath tlie horny plates on the jaws and disappear before 

 maturity, the molars are rooted (3 roots in the upper and 2 in the lower 

 jaw), and have enamelled crowns with two tuberculated transverse ridges, 

 they come into use gradually, there never being more than | functional 

 at the same time ; rostrum not bent downwards ; iipper Up bifid and 

 used in feeding ; vertebrae C6, D17, L2, C23 to 35 ; tail entire and rounded ; 

 manus with vestiges of two or three nails ; caecum bifid. Mainly fluvia- 

 tile, but also marine ; shores of and the great rivers emptjdng into the 

 Atlantic Ocean witliin the tropics ; 3 species on the American side and 

 1 on the African. AlUed extinct genera are Manatherium Hartlaub, 

 Oligocene, Europe ; Rihodon Am., OUgocene, Patagonia. Halicore Illig., 

 dugong, to 8 feet, i % m \^^ ; the anterior upper incisor is tusk-like 

 and projects in the male, but is not cut in the female, the posterior upper 

 incisor is found only in the young ; the lower incisors He beneath the horny 

 plate and are soon absorbed, the molars are without roots and enamel 

 and have tuberculated crowns wliich wear down to flat surfaces. The 

 rostrum of the skull is bent downwards. Vertebrae C7, D18-19, L and 

 C30. Tail notched and whale-like. Manus without nails. Caecum 

 single. Mainly marine, shores of the Red Sea, Indian Ocean, Australia, 

 3 species have been distinguished. Rhytina 111., Steller's sea-cow, 20-25 

 feet, recently extinct, about 1768, Beliring and Copper Islands in Behring 

 Straits, discovered by Behring and Steller, who were wrecked upon Beh- 

 ring Island in 1741. Its flesh and fat were exceedingly dehciovis, and it 

 was used as food by them and later mariners. Owing to its gentleness 

 and fearlessness of man, it was easily slaughtered and soon became extinct. 

 It was edentulous, had the horny pads on the jaws, was withovit nails 

 but had bristles on its manus. Its vertebrae had epiph5-ses. Hali- 

 therium Kaup, Oligocene of Europe, Eocene of America ; with large tusk- 

 like incisors in the upper jaw, f or f molars, well enamelled and tuber- 

 culated ridged crowns ; there appear to have been milk teeth ; sometimes 

 with normal but small nasal bones ; pehds better de-s-eloped with short 

 femur. A number of other genera are known from the Miocene and 

 Pliocene of Evirope and America. Prorastomus Ow., Eocene of Jamaica 

 and Europe is the oldest form known, with dentition i ^ c \ p and m %, 

 incisors not tusk-like. 



* According to Kiikenthal {loc. cit.) there are calcified rudiments of 

 canines in the lower jaw of the embryo, and of milk predecessors of some 

 of the teeth. 



