356 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



usually meet their end in rough water or storms soon after leaving 

 the rivers, but undoubtedly in rare instances natural rafts are de- 

 posited on distant shores with at least some of their crews in a viable 

 state. It is entirely conceivable that even tree frogs, which form 

 the greater part of the West Indian amphibian fauna, might occasion- 

 ally become unwilling sailors. Nor is it only rafts from rivers that 

 need be considered. Almost any kind of flotsam or jetsam of any 

 size is liable to be tenanted by some land creature, hanging on grimly, 

 if he is able, until the sea swallows him up. The millions and millions 

 of years of geological time surely allow enough for the (comparatively) 

 frequent wasliing up of rafts on distant shores and it is beyond 

 question that many islands have gotten their present faunas in this 

 way. But, I will remind you, nobody has ever attempted to explain 

 the distribution of freshwater fishes by the raft method! 



Great paleogeographical interest attaches to the fresh-water 

 fishes of the West Indies. Let us see what they tell us. 



WEST INDIAN FRESH-WATER FISHES 



The most striking feature of the fresh-water fish fauna of the 

 AVest Indies is the complete absence of members of the primary 

 division of fresh-water fishes, in particular the Ostarioph3'si, which 

 swarm in all the waters of North, Central, and South America. 

 Every West Indian fish to which the adjective "fresh-water" could 

 possibly apply belongs to my secondary division or to groups still 

 more partial to sea water. In this, the West Indies closely parallel 

 Madagascar, where not onlj'- is the primary division entirely absent, 

 but also the secondary ones that are present belong largely to the 

 same systematic groups as do those of the West Indies. 



To begin \vith, the rivers of the West Indian islands harbor a 

 number of fishes, belonging to purely or partly marine families, 

 which come up from the sea. There are gobies and eels and silver- 

 sides and gray mullets, some of which enter fresh water only occasion- 

 ally and some of which live in the rivers most of the time, returning 

 to the sea only to spawn. One of the most conspicuous and widely- 

 known of West Indian fresh-water fishes belongs to this category. 

 This is the mountain mullet (Agonostomus) , known in the Spanish 

 islands as dajao or lisa. There are three West Indian species, the 

 largest reaching a length of a foot, and others occur along the Carib- 

 bean coasts of South America, in Central America, and the Gala- 

 pagos.^^ A related genus (Joturus) lives in Cuba and Central Amer- 

 ica. It is not known whether the mountain mullets return to the 

 sea to spawn, but we do know that they belong to the marine family 

 of gray mullets, and that they and their companions, the eels, gobies, 



** Regan (190S) has revised the American spedes. 



