426 Evolution and Distribution of Fishes 



type from some other genus, probably Fundidus. For 

 Garman {262: 145) says: "Excepting the absence of ven- 

 tral fins in this genus, young specimens up to medium size, 

 resemble Ftindulus." We would explain its present geo- 

 graphic position as a genus, in terms of past geologic con- 

 ditions as follows : Species of Fundulus are widespread 

 over western Brazil, and must have existed there for a 

 long period. If one of these had nearly reached the west 

 coast, before final and pronounced elevation of the Andes 

 took place, such may have persisted in individuals that in- 

 habited lakes which were uplifted during the elevation pro- 

 cess. Isolated then in a new environment from allied forms, 

 it has in course of time split up into the ten species recorded 

 by Garman. 



With all respect to so painstaking an Ichthyologist as 

 Eigenmann, we are entirely at a loss to understand why he 

 should have regarded the 10 species of the genus, or the 

 associated catfish Pygidhim riviilatum, as In any way as- 

 sociated with a "marine character." Nor does Titlcaca In 

 any way suggest that it "was an arm of the sea. In which 

 its nearest relatives flourish." All of the Cyprlnodonts 

 are freshwater typically, and there Is no ground for con- 

 sidering that they had even remote ancestral connection 

 with the sea. 



The continuity of genera, both across the Isthmus into 

 Mexico and California, also across such West Indian islands 

 as have been already named, into Florida, Alabama, and 

 the S. E. States Is added proof that geologically a continu- 

 ous passage-way once existed in the west between the two 

 continents, at least since Eocene to Oligocene time, and that 

 in the east what are now scattered Islands were once more 

 or less connected, either as a continuous freshwater passage- 

 way, or as large islands that every now and again became 

 so connected as to exchange faunal — as they undoubtedly 

 have exchanged floral — types. 



As regards the Afro-Asiatic genera these are so closely 

 similar to American forms, that they have been regarded by 

 many systematlsts as generically alike, In the case of Cyprin- 

 odon and Fundulus. So striking is the relationship, and so 

 requisite is a land connection, that Eigenmann (26J: 523) 



