The Spine-finned Teleostei 393 



warm-temperate and ultimately temperate marine offshoot 

 passed across the N. Atlantis southern shore to the N. W. 

 African and later the west-central European shores. Mean- 

 while both families, amid the same environment as proved 

 stimulating to the Pomacentridae, became abundant inhabit- 

 ants of coral reefs, rocky shores, and algoid beds of the 

 eastern archipelago. 



The E-mbiotocidae, usually included in the Pharyngog- 

 nathi group of families, seem from many structural peculi- 

 arities to have been derived from two or even three distinct 

 types or genera of the Cichlidae. Thus the one freshwater 

 genus Hysterocarpus that in its single species H. traskii 

 is native to the lower reaches of the Sacramento river in 

 California, seems to be most nearly derivative from a series 

 now typified by Symphysodon and Pterophyllum of the 

 Cupai river in Brazil. The marine genera apparently ap- 

 proach most nearly to the living Brazilian Hygrogonus, no 

 other genus of the Cichlidae or of any other acanthopterous 

 group seeming otherwise to approach them. The 23 or 

 thereby marine species, are often abundant in shallow water 

 along the California coast, where they mainly feed on crus- 

 taceans. One genus however, Zalemhius, is now a deep-sea 

 fish (257: 1500, pi. 229), and as so often happens in such 

 environment, has developed large and prominent eyes. 

 Finally while most of the species of Ditrema are coastal 

 fishes from San Francisco northward to Vancouver, two 

 species have passed over, doubtless by the N. W. American 

 bridge, to Japan. 



So, small though the last family is, it strongly favors 

 direct origin from the large freshwater group of Cichlidae, 

 and still includes one freshwater species that makes close 

 generic connection with these. The remaining marine 

 species can only be interpreted at the present day as shore- 

 ward migrants from more primitive freshwater ancestors 

 that descended from the Cichlidae. 



The Gobiidae, that may next be treated, is of excep- 

 tional interest as being a family that fairly divides its 

 species between fresh- and salt-waters, with preponderance 

 toward the latter. The writer would recall Boulenger's 

 view that they "are not very remote from the Perciformes, 



