MATTHEW, XEW 8IRENIAN FROM PORTO RICO 



37 



the food. Various other specializations occur in the skull, carried con- 

 siderably further in the Dugong. 



A third line, closely related to the Dugong in most of its skull struc- 

 ture, but lacking the tusks, and with the reduction of the cheek teeth 

 carried to complete disappearance, is represented by the recently extinct 

 Rhytina of the Morth Pacific. 



A fourth and very distinct line is represented by an imperfectly known 

 genus Desmostylus found in the Miocene of Japan, California and Ore- 



FiG. 2. — 1 Halitherium antillense, parts of cervical (right) and anterior dorsal (left) 

 vertebrce of type specimen 



Posterior views, half natural size. 



gon. In this the skull retains more of its primitive proportions, while 

 the tusks are large in both upper and lower jaws and the cheek teeth 

 become hypsodont or high-crowned and of a very curious pattern. 



Halitherium is generally accepted as an ancestral Dugong. Eotherium 

 Owen, JEosiren Andrews, Protosiren Abel, Archceosiren Abel, all from the 

 Eocene of Egypt, are a closely related group of genera, all but the first due 

 to. the activity of recent investigators in the Fayum faunas, especially 

 Andrews and Abel. They represent collectively a primitive stage in the 

 Dugong line. 



Place of Oeigiist of the Dugongs 



As the Manatees have not been found outside the Atlantic Basin, it is 

 commonly assumed that they originated there or else migrated from the 

 Tertiary Mediterranean Basin. The oldest fossil Dugongs being found 

 in Egypt and Italy, later stages in Germany, France and Belgium, the 

 modern forms in the Eed Sea and Indian Ocean, it has been assumed that 

 they originated in the Mediterranean Basin, found their way to the north 

 European shores and in the opposite direction into the Indian Ocean, 

 and thence perhaps finally to the North Pacific, but never reached the 

 western coasts of the Atlantic. 



The discovery here presented would seem to show that the distribution 

 of primitive Dugongs in the North Atlantic was wider than was sup- 



