164 ORIGIN OF LIFE IN AMEEICA 



affinity between Europe and North America is so strong, 

 and already so many instances of this relationship have been 

 referred to, that nothing short of a wide and convenient land 

 bridge with lakes, rivers and mountains will suffice to ex- 

 plain the meaning of the palaeontological facts. All we know 

 is, that in early Tertiary times these fishes multiplied and 

 migrated from their original centre of dispersal. The genus 

 of the bow-fin is all but extinct. Only a single species 

 remains. The bony-pikes exhibit a little more vitality, no 

 less than three species being still living. The common form 

 (Lepidosteus osseus) ranges from the Great Lakes to Vermont 

 in the east, and from there south-westward as far as Mexico. 

 A much larger bony-pike lives in the southern States, in 

 north-eastern Mexico and in the island of Cuba, while a 

 smaller species (L. tropicus) has been observed in Tabasco, 

 Guatemala, Nicaragua and Panama.* If Lepidosteus were a 

 fish directly limited to fresh water, we might argue that at 

 some remote time in the past, a land mass extended from 

 Mexico to Cuba and southward to Panama, but being occa- 

 sionally met with in brackish water it is possible that bony- 

 pikes can traverse short distances by sea. We cannot for this 

 reason base any conclusions regarding minor changes of land 

 and water on the present distribution of these fishes. Never- 

 theless it is a significant fact that the western States '.are. 

 devoid of bony-pikes and perches as they almost are of fresh- 

 water Unios. 



Besides the Mississippi fauna, the curious dwellers of sub- 

 terranean waters in the Mississippi drainage area throw a 

 certain amount of light on the past conditions of the country. 

 A brief account of them at any rate will be of interest before 

 concluding this chapter. 



I believe Mr. Putnam f was the first to exhibit a collection 

 of blind fishes and crustaceans from the Mammoth Cave to a 

 scientific meeting. In doing so he expressed the opinion 

 that most of the animals inhabiting the cave are of compara- 

 tively late introduction, since they are closely allied to forms 



* Began, C. Tate, "Biologia Centrali- Americana," p. 181. 

 t Putnam, P. W., " Mammoth Cave and its Inhabitants," pp. 194 

 195. 



