394 Evolution and Distribution of Fishes 



and may have evolved out of a type not very different from 

 the Percidae" (2:688). Jordan's position therefore seems 

 scarcely justified when he says (25^:459) that they have 

 "no near relations among the spiny-rayed fishes." Reasons 

 will gradually be given below, as well as later for the 

 writer's position, in seconding Boulenger's conclusion. 



The family is a large one, being made up of about 30 

 genera and 600 species. If one tries to construct a picture 

 of the average external and internal structure of a primitive 

 genus of the family, it can be said that the composite type 

 conforms closely to such percoids as Boleosoma, Etheosto- 

 ma, Ammocrypta, and Crystallaria of the group Percidae, 

 all of which inhabit the east-central or southern U. States. 

 Further, we would regard Eleotris as the primitive gobioid 

 for the following reasons. The living Gobiidae, as sub- 

 divided by Giinther, include four groups : ( i ) The Gobiina 

 section with two separate dorsal fins, and ventral fins dis- 

 tinct or fused to form a disc; (2) the Amblyopma section 

 with a fused and continuous dorsal fin and ventrals united; 

 (3) the Trypatichenina section with continuous dorsal fins 

 and disconnected or fused ventrals; (4) the CaUionymma 

 section with two separate dorsal fins and ventral fins widely 

 apart. Eleotris falls under the first section, for in its fin 

 structure and many other morphological details, it shows 

 closest aflinity to the percoids named. 



Now, upwards of 50 species of Eleotris are known, 

 mostly from tropical and sub-tropical, more rarely tem- 

 perate areas. Of these 30-32 are freshwater, 6 show great 

 adaptability for living in freshwater or brakish or marine 

 coastal regions, while 13-14 are marine. But 9 of the 

 species are still found in freshwaters from Mexico and 

 Lower California eastward to San Domingo and Cuba, 

 also southward to the Equator and Guiana. One is found 

 in Mascarene rivers, while another {E. fusca) resembles 

 it, but also becomes more or less coastal-marine and appears 

 in Mauritius, thence on to Polynesia. Now did we not know 

 the structure, general habitat, near afl'inities to American 

 percoids, and the distributional trend of the entire genus, 

 we might have readily supposed that E. fusca was a primi- 

 tive type, which was gradually passing into freshwaters, also 



