310 SIRENIA. 



Sub-Ord. SIRENIA. Herbivorous Cetacea. 



Nostrils opening in the u^Dper lip. Teeth of two kinds ; incisors pre- 

 ceded by milk-teeth, and molars with flat crowns. Two pectoral mammae. 

 Body slightly hairy, and bristly moustachios on the lips. No hind limbs. 

 Posterior part of body ending in a horizontal cartilaginous fin ; anterior 

 limbs in the form of fins or flappers. 



The bones of the skull are dense and massive, aud the intermaxillaries 

 large. They are only loosely connected together, and this, with the generally 

 dense nature of the other bones, and their not having medullary cavities, 

 shows a reptile-like condition. There are traces of pelvic bones in all. The 

 bony nostrils open near the summit of the cranium. There is a short but 

 distinct neck. The number of ribs is large — nineteen pairs in some. The 

 stomach is divided into four sacs, of which two are lateral ; they possess 

 a large caecum, and the intestinal canal is long. 



The hei-bivorous Cetacea approach in structure perhaps nearest to some 

 of the pachydermatous Ungulata, near which they might have been placed, 

 but I have thought it more advisable to bring them in here at the con- 

 clusion of the order Ungulata. They feed entirely on plants, either plucked 

 at the bottom of the sea, or on rocks laid bare by the retreat of the tide, 

 and they do not venture far out to sea, but keep near the shore and the 

 mouths of large rivers. 



Their pectoral mammae, and the peculiar physiognomy of these animals 

 as observed when they raise their bodies partially out of water, have pro- 

 bably led to the fabulous accounts by mariners of Tritons, Sirens, and 

 Mermaids. 



One species has been observed on the southern coasts of India. 



Gen. Halicore, Illiger. 

 Syn. Bugongus, Tiedimann. 



Char. — Two large upper incisors in the adult : none in the lower iaw. 

 No canines. Molars - — - in the young, fewer in the adult, flat; body 



elongated ; pectoral fin without claws ; caudal fin lunate, broad. 



The incisive teeth assume the form of pointed tusks, but are nearly 

 covered by the thick fleshy lips, which are bristled with moustaches. 



The milk incisors are stated by Kelaart to be , and in the adult 



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