THE DUGONG 337 



form ; there appears to be but a single species, though more than 

 one name has been given to supposed distinct species. As already 

 mentioned, it differs from the Manatee in the possession of a 

 Whale-like tail ; the nostrils, too, are more upon the upper surface 

 of the head, and there are no nails upon the flipper. The peculiar 

 cleft lip of the Manatee is not so well developed in the Dugong, 

 but there are traces of it ; and in the foetus the likeness to the 

 Manatee in this respect is very striking. It would thus appear 

 that Halicore is a stage in advance upon Manatus; that the 

 remarkable mechanism of the lip of the latter has been possessed, 

 but has been lost, by the Dugong. The skull of the Dugong is 

 distinguished by the stout premaxillary bones, which bear a tusk 

 in the male. In the female the tooth is there, but is lodged within 

 the bone. This incisor has a milk forerunner. The back teeth 

 of the Dugong (there are no canines) are few in number (four or 

 five, even six), thus showing a gradual reduction when compared 

 with Manatus ; and this culminates in the toothless Rhytina. It is 

 also interesting to notice that in the massive lower jaw there are 

 traces of an incisor. Were this to be developed into a tusk, the 

 jaw would present a curious resemblance to that of Dinotherium. 



The Dugong, H. dugong, has the reputation of being the 

 original of the mermaid legends, since the young is held to the 

 pectorally-situated breast with one nipper. " But it should be 

 remembered," justly observes Dr. Blanford, " that stories of 

 beings half man or woman, half fish, are as common in temperate 

 as in tropical seas, and that some of them are more ancient than 

 any European knowledge of the Dugong." 



Extinct Sirenians. The earliest genus that can be with 

 certainty referred to this order is the Oligocene Prorastoma. 

 This genus, though offering no particular skull-characters that 

 assist in the determination of the much-debated affinities of the 

 Sirenia, shows a remarkable condition of the teeth that may 

 afford a clue. The species P. veronense, recently described by 

 Mr. Lydekker, 1 is founded upon a fragment of the skull which 

 contains two teeth apparently representing the third and fourth 

 upper milk molars. The interest attaching to these teeth lies in 

 the fact that they clearly exhibit the buno-selenodont condition 

 characteristic of certain early Artiodactyles, e.g. Merycopotamus. 



Halitherium is a later genus, which is known- by the nearly 



1 Proc. Zool. Soc. 1892, p. 77. 

 VOL. X z 



