Geographic and Geologic Relations 413 



But another marine invasion westward, along the north- 

 western shores, and later by the wide bridge that Koken 

 and others accept as having then existed between America 

 and east Asia, would explain the present location of species 

 from Japan southward even to Australia. In the last 

 chapter we outlined what appear to be the derivative fami- 

 lies that in turn branched off from the Berycidae as marine 

 dwellers. 



From the geographic and geologic standpoints then, we 

 would anew affirm that all present evidence points to origin 

 of the Acanthopterygii in freshwater expanses of late Com- 

 manchean age, and over the north-central part of the North 

 American continent. The Percopsidae, as represented by 

 the two living genera Percopsis and Columbia, also the 

 Aphredoderidae, as alone represented now by Aphredo- 

 denis, constitute the annectant types, that point backward 

 to Salmonidae-Clupeidae as predecessors, and forward to 

 the Percidae, Centrarchidae, a'nd Berycidae as evolved 

 descendants. 



If it be accepted that the chart-figures 35 (p. 240) and 

 66 (p.381 ) set forth approximately the relation of land and 

 sea areas that have above been traced, in connection with 

 acanthopterygian fish-life, a satisfactory basis is got for ex- 

 planation, in large part, of the distribution of the soft-finned 

 and undoubtedly more primitive teleosteans. 



The freshwater family Siluridae, with about 1000 

 species, is highly instructive in its general as well as in its 

 sub-family distribution. Divided by Boulenger into eight 

 sub-families, that which we would regard as probably the 

 most ancient is the Bagrinae, which includes the greatest 

 number of genera, as well as the fossil genera, Amiurus, 

 Arius, Macrones, and Rita, that still have living repre- 

 sentatives. Ariiis moreover has been recorded in Mid- 

 Eocene to Mid-Oligocene strata from East Brazil, England, 

 and Germany, also in more recent (?Pliocene) strata of 

 Madagascar and the Siwaliks of India. It is the genus 

 likewise that now includes by far the largest number of 

 species — upwards of 70. Their present distribution also 

 is remarkable. For they occur in rivers of the Southern 

 States, in Porto Rico, Panama, Guatemala, West Indian 



