326 MAMMALIA. 



Order SIRENIA. 



Mammals of herbivorous and aquatic habits, with an almost hair- 

 less skin, a horizontal flattened caudal fin and an odontoid process ; 

 no sacrum ; the capitulum of the rib articulates with the centrum 

 of the vertebra; no claws ; fore-limbs paddle-shaped with rudimen- 

 tary nails ; digits never provided with more than three phalanges; 

 no trace of hind-limbs ; brain-case cylindroidal ; the parietals 

 meet in a sagittal suture ; the rami of the mandible have a high 

 ascending portion (in these two points differing from Cetacea) ; 

 frontals with large supra-orbital processes; nasals aborted; salivary 

 glands well developed ; a caecum present ; testes abdominal ; mam- 

 mae pectoral. 



Genus HALICORE. 

 Halicore, Illiger Prodr., p. 140 (181 1). 



Halicore dugong. 



Trichechus dugung, Erxlehen Syst. Reg. Anim., p. 599 (1777). 



Halicore dugong, Illiger Prodr.,'^. 140 (1811) ; Gray Illustr. Ind. Zool., ii, 



pi, xxiii ; Horsfield Cat. E.l. Mus., p. 139; Blyth Cat. no. 461, p. 143; 



Jerdon Mamm., no. 240, p. 311; Blyth y. A. S. B., xliv, Burma List, p. 



53 ; Nemll Taprobanian, i, p. 2. 

 Halicore indicus, Desmarest Mamm., p. 509 (1822) ; Cantor J. A. S. B., xv, 



p. 274 ; Kelaari Prodr. Faun. Zeylan., p. 89 ; Blyth y. A. S. B., xxviii, 



p. 494. 

 Halicore tabernaculi, RUppell and Sommerring Mus, Senckenb,, i, p. gg, pi. 



vi (1834). 



Distribution. — The coasts of the Indian Ocean from Mozam- 

 bique to the Red Sea, Malabar, Ceylon, Andamans and Tenas- 

 serim to Singapore. 



The Australian species was separated by Owen, chiefly on ac- 

 count of the fact that it possessed 24 instead of 20 molar tpeth, this 

 does not seem to be a constant difference, as both species excep- 

 tionally develope 6 molars instead of 5. 



There seem to be, however, other distinctions, some of which 

 were noticed by Owen, these distinctions have been ignored by 

 modern writers by whom all the Dugongs are included under one 

 specific name. If an Australian skull be compared with an Anda- 

 manese one of approximately the same age, it will be found that 

 the very large external nasal opening is in the Australian skull 

 distinctly heart-shaped, the sides of the opening forming a conti- 

 nuous curve; in the Andamanese skull the opening is pear-shaped, 

 the sides of the opening bulging forward anteriorly so as to con- 

 strict the opening; in the Australian skull too, the anterior projec- 

 tion of the frontal bones which, with the premaxillse and the maxillae 



