204 A^'^.\L.'^ xi:\v yoi'k icm/j/:i/v or ><ciences 



hypothesis may reasonably tx- invoked. ■■■ Tlu' liippopotHini may have 

 arrived by swiinniiiig and tlie bush-])ig and the slirew may liave been 

 introduced by man, while the bats may readily iiave arrived by flight. 

 The extinct ground birds are easily derived from flying birds. 



Dr. Arklt,^^ in his discussion of the .Malagasy I'auna, points out its 

 composite character, derived from several successive invasions. 'I'his, I 

 think, is clear enough; but it seems equally clear that these were not 

 faunal invasions due to land connection but sporadic colonizations by a 

 few species all at dift'erent times. The characters of the mammalian 

 fauna, both negative and positive, practically exclude the theory of larul 

 connections during the Tertiary. 



The West Indian islands alTord another marked instancL'. In spite 

 of its nearness to Florida, there are no North American mammals in 

 Cuba, except the manatee, — analogous with the hippopotaniTis in Mada- 

 gascar. Nor are the other islands richer in fauna. As also in Mada- 

 gascar, we have a peculiar and very ])rimitive insectivore Solenodon 

 (Cuba and Hayti), a number of peculiar extinct ground-sloths, of which 

 Megalocnus is the best known, and wliidi although Pleistocene in age 

 are derivable not from the Pliocene or Pleistocene ground-sloths of North 

 or South America but from the Miocene ground-sloths of Patagonia, 

 and evidently diiferentiated through a long-continued period of isolated 

 evolution, and a couple of chinchillas — the hutias of the larger islands, 

 the (extinct) A nihJyrhiza in Anguilla. The Solenodon may be referred 

 to a more ancient colonization, the ground-sloths probably arrived during 

 the Miocene, the chinchillas more recently; and the direction of the 

 prevalent ocean currents points out the reason why these are of South 

 American derivation. Those who, like Dr. d. W. Spencer,^^ believe in 

 gigantic elevation movements connecting the Antilles with the mainland 

 in Pliocene and Pleistocene would account for the absence of the conti- 

 nental fauna by invoking a subseqiient subsidence which drowned out 

 everything else. The improbabilities involved in this hypothesis on strati- 

 graphic and faunal grounds have been pointed out by W. TI. Dall, U. T. 

 HilP" and others. 



^3 The moist tropical conditions of early Tertiary times wotild favor tlie formation of 

 svicli rafts, the small size and ai'boreal habits of the animals concerned would increase 

 the chances of their lieins ca\if;ht on such rafts and the uniform climal(> and conse- 

 quently more placid seas would increase the distance over which the raft might be trans- 

 ported before it broke up. 



•'* 'I'lncoDORE AuLDT : Entwickluns der Konlinenle und ilircr I.ebewelt. ])p. 110-142. 

 1007. 



"■'■ .1. \y. SPENCioit : "Ueconstruction of the Antilleau Continent." Itull. Geol. Soc. Anier., 

 vol. vl, pp. 103-140. ISO."). 



^^ W. II. Dall: "Geological Results of thi> Study of thr Tertiary Fauna of Florida." 

 Trans. Wagn. Inst., vol. iii, pt. vi. 1903. 



R. T. Hill : "Geological History of the Isthmus of Panama and Portions of t'osta 

 Rica." P.ull. Mus. Oomp. Zo51.. vol. xxviii. pp. 151-285. 1808. 



