494 THE AGE OF MAMMALS 



representatives of the remarkal)le Pliocene mammal known as Desrnostylus 

 (see p. 344), Favoring the less probable theory of transatlantic migration 

 from the African coast is the presence in supposed Eocene deposits of 

 Jamaica of one of the most primitive of sirenians, the Prorastomus of Owen.^ 

 This animal, with its comparatively straight or normal upper jaw and com- 

 plete series of teeth, is even more primitive in structure than the Eosiren 

 libijca of the Upper Eocene Mokattam limestones (Fig. 89) of the Cairo 

 and Faj^um districts of Africa. 



The great northern sea-cow of the Pacific {Rhylina stelleri), or Steller's 

 sea-cow, was discovered by Steller, v/ho accompanied Behring on his last 

 expedition of 1741 in search of the northwest passage.^ It inhabited the 

 shallow waters immediately surrounding certain of the Aleutian Islands, 

 and moved by means of tAvo small anterior flippers, which were covered 

 with bristles, and by its fluked tail. The short fore leg terminated abruptly 

 without fingers or nails, but was overgrown with a number of short, thickly 

 placed brush hairs. It was a bulky animal, thirty or even thirty-five feet 

 in length, and twenty feet in girth, weighing about 6,700 pounds, and covered 

 with a very thick, much wrinkled skin of a dark brown color. Of all the 

 Sirenia it Avas the only one adapted by its thick undercoating of blubber to 

 inhabit the cold seas of the north. In Pleistocene times it probably ranged 

 much farther south than the Aleutian Islands. It probably became extinct 

 toward the end of the eighteenth century because it fell an easy prey to 

 the sailors and fur traders. 



Antiquity of Man in North America 



The time of the first appearance of man on the North American con- 

 tinent still remains to be determined, and is a problem of the very highest 

 importance. 



Was man contemporaneous with the closing period of the second or 

 Megalonyx fauna, or with the third, the Ovibos and late Mastodon, fauna? 

 Did man enter this country from Asia or from South America? Are traces 

 of human occupation found first on the Pacific or on the Atlantic coast? 

 All these are questions which remain yet to be answered positively. 



In brief, it may be said certainly, so far as anatomical evidence is con- 

 cerned, that no trace of human skeletons of the Palaeolithic or Neandertal 

 type of Europe have been found in North America, and as certainly that 

 all skeletons which have been reported have been referred finally to the 

 recent Indian type. Second, there is some evidence of the coexistence of 

 man with the late stages of the Megalonyx Zone in California and in the 



* Owen, R., On Prorastomus sirenoides. Quart. Jour. Geol. Soc. London, Vol. XXXI, 

 1875, p. 559, PI. 18 and 19. 



2 Nordenskiold, A. E., The Voyage of the Vega round Asia and Europe, with a Historical 

 Review of Previous Journeys along the North Coast of the Old World. Translated by Alex- 

 ander Leslie. New York, 1882. 



