340 GEOGRAPHICAL AXD GEOLOGICAL DISTRIBUTION. 



restricted to the East African coast and the Red Sea, another (Hali- 

 core dugong) inhabits the Indian and Pacific oceans, eastward from 

 the home of the last to the Philippines, and the third (Halicore 

 australis) the waters of Eastern and Northern Australia. 



Fossil remains of sirenians, although not very numerous, occur 

 throughout all the Tertiary formations, from the Eocene to the 

 Pliocene, inclusive. The earliest forms are the Eotherium ^Egyptia- 

 cum and Manatus Coulombi, from the Mokattam limestone of Egypt, 

 Hemicaulodon effodiens, from the basal Tertiary beds of Shark 

 River, New Jersey, and the somewhat doubtful Halitherium du- 

 bium, from the deposits of the Gironde, France. In the last-named 

 genus are included a considerable number of species from the Mio- 

 cene deposits of Germany, France, Belgium, and Italy, and a single 

 undetermined (?) form from the Isthmus of Suez. Felsinotherium 

 and Chirotherium are Pliocene forms from Central and Northern 

 Italy, and Rhytiodus Capgrandi a species from the nearly equivalent 

 deposits of the Garonne, France. The American fossil sirenians 

 comprise, in addition to the Eocene Hemicaulodon, two or more 

 species from the Miocene deposits of South Carolina, Manatus an- 

 tiquus, M. inornatus, and Dioplotherium Manigaulti ; the first also 

 occurs in New Jersey and Virginia. Of the Post -Pliocene forms 

 the best known is the Rhytina gigas or Stelleri, " Steller's sea- 

 cow," an animal which appears to have been fairly abundant about 

 Behring and Copper Islands as late as the second half of the last 

 century, but which is now apparently entirely extinct. The im- 

 bedded remains occur principally in the raised beaches and peat- 

 mosses of Behring Island. 



Woodward calls attention to the significant fact that, if we 

 " take the belt of the tropics, that is, 23 N. and 23 J S. of the 

 Equator (or, better still, say 30 N. and S. of the Equator), we shall 

 cover the geographical distribution of all the living sirenians. If 

 we take another belt of 30 north beyond the Tropic of Cancer, we 

 shall embrace the whole geographical area in which fossil remains 

 of sirenians have been met with. Assuming, as I think we may, 

 that the Sirenia at the present day belong exclusively to the tropi- 

 cal regions of the earth, and that Rhytina, in its boreal home, was 

 simply a surviving relic from the past (a sort of geological ' out- 

 lier,' as of a stratum elsewhere entirely denuded away), we must 

 conclude that the presence of about twelve genera and twenty- 



