290 ORIGIN OF LIFE IN AMERICA 



number of absentees and peculiar species among the birds, 

 as in other groups. Dr. Chapman* is evidently puzzled how 

 to account for the avifauna. Nevertheless, he makes the 

 remarkably suggestive statement that if it could be shown 

 that Central America was cut off from both continents at the 

 time when it was joined to the West Indies, the origin of the 

 island fauna could be explained in a satisfactory manner. 

 That is precisely, I think, what did happen, as I have indicated 

 above. 



Cuba presents some special aspects of interest. We have in 

 the first instance quite a remarkable assemblage of fossil 

 mammals. Western Cuba, with its extensive limestone dis- 

 tricts, abounds in caves, many of which contain stagnant 

 water or running streams. One of the most remarkable fea- 

 tures of these subterranean waters is that they are tenanted 

 by two kinds of fishes belonging curiously enough to a family 

 of deep-sea forms (Brotulidae). These species, Stygicola 

 dentatus and Lucifuga subterraneus, moreover, are blind, 

 as might be expected from their habitat. Another typically 

 marine genus, Atherina, possesses a single fresh-water species 

 (A. evermanni) which is only known from western Cuba. 

 Whether the presence of these marine species in fresh water 

 implies that western Cuba had been submerged below sea- 

 level is a debatable question that need not be further pur- 

 sued. Other Cuban fresh-water fishes are forms often found 

 in brackish water, or marine forms migrating into fresh water. 

 Besides these there are two species of Heros, a Symbranchus, 

 a Lepidosteus and one Agonostomus, all of which belong to 

 purely fresh -water groups that could only have reached Cuba 

 by means of a continuous system of lakes and rivers between 

 the mainland and the island. Heros tetracanthus and Heros 

 nigricans are members of the family Cichlidae, which has a 

 wide range in South and Central America, only a single 

 species entering the United States. Agonostomus monticola 

 has a wider distribution in the West Indies, and is also met 

 with in Mexico. Lepidosteus tristoechus lives in Mexico and 

 the southern States, while Symbranchus marmoratus is widely 

 distributed in the fresh waters of tropical America. If, as 



* Chapman, F. M., " West Indian Bird Life," p. 330. 



