486 Evolution and Distribution of Fishes 



communication existed over a great northern continental 

 mass. This evidently extended from central North America 

 eastward to east Asia, and even for a time, in the late 

 Jurassic period, into Australia. 



Alongside the above in some of their habitats, were 

 the even more primitive protospondylic fishes, that make up 

 the Amiidae, Eugnathidae, Macrosemiidae and Semiono- 

 tidae. The first of these is still represented by the one 

 living species Amia calva of N. America, while the genus 

 passes back, in the same area to at least early Eocene. This 

 anew demonstrates the correctness of the view, advocated 

 by Cope, Leidy and successors, viz. that a large part of 

 central and west-central N. America has undergone little 

 profound change since the Eocene, though slow denudation 

 action, that permitted the fishes to exist and readapt them- 

 selves amid such changes, were steadily going on. 



But the fact that species of Amia occur in upper Eocene, 

 and in Oligocene-Miocene beds of France, Prussia, and 

 Bohemia, is proof that some mode of freshwater communi- 

 cation existed during the Eocene between America and 

 Europe. It would be a mistake however to suppose — at 

 least with present knowledge — that the entire group Ami- 

 idae originated in the western Continent. For the related 

 but much older genera Megaliiriis and Liodesmus are only 

 known from Jurassic beds of S. W. Europe, if we accept M. 

 mawsoni that Woodward has described {304: Sj) from 

 the freshwater cretaceous of Bahia in Brazil. The parallel- 

 ism between this distribution, and a similar one referred to 

 above, as well as of others that follow, strongly indicates 

 that the same land-masses existed, and similar lines of 

 travel were taken, by different groups of fishes. 



Known facts then favor the view that the Amiidae 

 evolved during early or mid-Jurassic time in lakes and river 

 areas of west-central Europe, and persisted there till at 

 least Lower Miocene days, when they disappeared from 

 that region during the mid or upper Miocene. Representa- 

 tives travelling westward however, during the Cretaceous 

 period, to N. America spread widely there, and of these 

 Amia calva still persists, while Megalurus^ pursuing a line 



