256 ANNALS NEW YORK ACADEMY OF SCIENCES 



SIRENIA 



The most primitive sirenians are found in the late Eocene of Egypt. 

 As these were apparently contemporary with more prog-ressive types in 

 the jVliddle and Upper Eocene and Oligocene of Europe, they indicate, if 

 anything, that the Mediterranean shores lieid a less progressive fauna 

 than the North Atlantic. The Oligocene and Miocene types are approxi- 

 mately ancestral to botli the modern groups, manatees and dugongs. Ap- 

 parently the manatees became characteristic of the North Atlantic, the 

 dugongs of the Indian Ocean shores. The progressive cold of the later 

 Tertiary and Pleistocene has driven the manatees out of the Arctic and 

 northerly Atlantic shores and their northern limit is now Florida on the 

 western, and the African coast on the eastern side. They have not been 

 found fossil north of 40° N. lat. on the American coast,'** for the excel- 

 lent reason that there are practically no Tertiary littoral deposits north 

 of that latitude. 



The occurrence of Manatus in West Africa and in the West Indian and 

 South American coasts is among the arguments used in support of a 

 transatlantic bridge ; but there is no evidence at all that the ancestors of 

 Manatus did not inhabit the whole of the North Atlantic and Arctic 

 basin during the Tertiary. It is certain that they did inhabit parts of 

 the intervening European and American littoral, and the negative evi- 

 dence elsewhere is obviously worthless, because there are no formations 

 known in which they might be fomid. 



CONDYLAKTHRA AND SPECIALIZED SUCCESSORS 



We may here consider the distribution of a number of extinct groups 

 of Tertiary ungulates or semi-ungulates, whose rise and culmination took 

 place at an earlier epoch and under different conditions from those which 

 we have discussed. The Condylarthra are an extremely primitive group 

 of hoofed mammals, fulfilling nearly the theoretical requirements for the 

 common ancestral type of all placental ungulates. The earliest known 

 artiodactyls and perissodactyls are, however, too much specialized to be 

 immediately derived from the known Condylarthra. Condylarths first 

 appear in the Paleocene of North America and Europe and in South 

 America in the Notostylops fauna, here regarded as Eocene. In North 

 America, they develop through the Taligrada into the Amblypoda, culmi- 



"> For distribution of manatees during Tertiary vide Ha5', Bibl. Foss. Vert. N. A., U. S. 

 G. S. Bull. 179, p. 583-4, 1902 ; of Old World Sirenians, Abel, 1904. Abb. Geol. Reich- 

 sanst., xix Bd., s. 214 ; 1906, N'eues .lahrb. Ed. ii, s. 50-60 ; 1912, Palaeontographica, 

 Ux Bd., s. 292. 



