Liberia <^ 



this is a remarkable fact, as it shows either that the manatee 

 must have been able to scramble up and over the rocks of 

 the Niger rapids between Busa and Sai so as to reach the 

 placid waters of the upper stream from the Gulf of Guinea, 

 or else that its presence on the Upper Niger is a sign of its 

 extreme antiquity in that region, as it may have remained in 

 these waters from that undetermined period of the Tertiary 

 epoch when the northern basin of the Niger was an inland sea 

 communicating with the Atlantic. 



In any case, the existence of the manatee in all the rivers 

 and estuaries of West Africa is another fact which goes to 

 support the theory of a land bridge connecting West Africa 

 with South America as lately as the end of the Eocene Period. 

 From such evidence as we have before us at the present time 

 the isolated order of the Sirenia, to which the manatee and 

 dugong belong, originated in the lands bordering the Gulf of 

 Mexico. In Jamaica fossil remains have been found of an 

 ancestral type connecting the present Sirenia with some primitive 

 mammalian group (near the base of the elephants and ungulates) 

 that had the normal mammalian formula of teeth — Incisors, 

 canines, and molars. From this area of distribution in the early 

 Eocene arose the Dugong, which no doubt made its way from 

 the western coasts of America across the Pacific to Eastern 

 Asia and Eastern Africa, leaving relations behind on the 

 Northern Pacific coasts (like the Rhytina) ; and the Manatee, 

 which extended its range through the West Indies to the 

 eastern coast of South America, and thence by some chain of 

 vanished islands, or even by the Eocene isthmus, across to 

 West Africa. It is doubtful whether the Manatee could 

 make such a long journey across the ocean as that from 

 Brazil to West Africa. Even if it could change its diet from 

 fresh-water vegetation to seaweed, it would scarcely survive the 



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