8 FRESH-WATER FISHES OF SOUTH AMERICA EIGENMANN. 



The Characinidce also here attain their greatest development. There 

 are sixty-one geuera of four hundred and thirty-five species. 



The Eryihrlmmv are without an adipose fin. 



The Curimatlmv are edentulous, or have the teeth feebly developed. 

 They differ from the Citharininw (African) chiefly in having a shorter 

 dorsal fin. 



The Anostoniatinw have a short dorsal fin, narrow gill-opening, and 

 remote uares, the teeth being well developed. 



The Tctragonopterime and Hydrocyoiiincv differ \n the character of the 

 teeth, the former having broad notched, the latter conical teeth. The 

 dorsal fin is rather short in both. Both reach their greatest develop- 

 ment in South America. There are in South America eighteen genera 

 of oue hundred and fifty -nine species of Tetragonopterinw and but 

 four genera of twenty-nine species in Africa. Of the Hydrocyonince 

 there are eleven genera of fifty-four species against two genera and 

 five species in Africa. 



The Gremichince consist of two genera of one species each, found re- 

 spectively in South America and Africa. 



The Serrasabnonincv are characterized by the large teeth and serrated 

 belly. 



The CichUdw is another family which reaches its greatest develop- 

 ment in South America. 



THE ORIGIN OF THE SOUTH AMERICAN FAUNA. 



The species of marine families need, in this connection, only a pass- 

 ing notice. Many of the species live habitually in the sea and enter 

 rivers only occasionally. The families having strictly fresh- water species 

 or genera are the Dasyhatidce, Cyimnodontidce, Belonidcv^ Muf/ilidce, 

 Serranidw, Scicimidw, Batrachid(v, and Tetraodontidw. Some of these, 

 as the genus 0r<istias, are evidently of very long standing. This genus 

 of four species confined to Lake Titicaca was evidently long ago — long 

 before the Andes had reached their present height — separated from the 

 ordinary forms inhabiting brackish water. Other genera belonging to 

 this category are : Protlstius Cope, a genus intermediate between the 

 Mn g ill da> and the Cyprinodontidce found in the Peruvian Andes at an 

 elevation of 12,000 fee', and Gastropterus Cope {Mugilidw) from the 

 Pacific slope of Peru at an altitude of 7,500 feet. 



The genera Percichthys and Percilia have also been long enough 

 separated from their marine ancestors to become generically distinct. 



The fresh-water genera and species of Belonidce, Scicenidcv, Batra- 

 chid(e, and Tetraodontidw live chit-fly in the lower courses of rivers and 

 are probably older additions from the sea. 



The Lepidosirenida', a family of few genera ajd species, is evidently 

 now in its last stages. No fossils of Lepidosiren have yet been found. 

 The Dipnoi made their appearance in the Triassic (Permian; Bohemia, 

 Texas). "Eemains of Ceratodus have been found throughout the en- 



