10 FRESH- WATER FISHES OF SOUTH AMERICA EIGENMANX. 



the present Xortb Americau forms are, not unlikely, lineal descend: 

 ants.* 



As the Silurince and Pimelodime were already differentiated near the 

 beginning of the Tertiary, the Diplomystidw must have originated still 

 earlier. 



The Tachisurime were the first to be differentiated from the Diplo- 

 mystidce. How close the existing intergradation between them may be 

 can not be told from the imperfect knowledge of Paradiplomystes, etc. 

 They most probably arose in South America. At present the species 

 are chiefly marine and it is not unlikely that several other subfamilies 

 besides the Pimelodince are directly derived from them. 



The Pimelodiiue are Tachinurinw with remote nares. They now flour- 

 ish most where they probably had their origin. From the Pimelodince 

 have been derived directly or indirectly a number of subfamilies and 

 families. The furthest development in one direction has been reached 

 by the Aspredinidce, while the development in the other direction 

 culminates in the Loricaridce. There does not seem to exis' a sufflcient 

 break in the South American series to warrant the supposition that 

 any of the subfiimilies were developed elsewhere and have immigrated. 

 They all must be autochthons of the neotropical region. 



The Eventognatki and Gymno)ioti form, with the order just considered, 

 the siiperorder Ostariophysece of Sagemehl, which is distinguished from 

 all other orders and superorders by the presence of a Weberian appa- 

 ratus, or ossicula auditus, connecting the air bladder with the auditory 

 apparatus. Some of the non-American families of the Uventognathi 

 approach so closely to the Nematognatlii that Yalenciennest had at one 

 time some doubt whether Pygidium, a South American genus of Nema- 

 tognathi, should not be placed with the Cobiiidce. The common descent 

 of the three orders of Ostariophysece may be conceded. The Eventog- 

 nathi seem to differ from the Xematognatki in the possession of a sub- 

 opercle. 



In the north temperate region tbree families of Eventognathi have 

 become differentiated. In the tropics the order is represented by the 

 family Characinidie. The subfamilies ^rj/^^riHinre, Curimatime, Anos- 



"Dr. Jordan (Science Sketches, p. 100) says: "The catiishes of [North] America 

 are all probably ilescendants of a commou stock, not allied to South American 

 forms, but probably finding its nearest relatives in India. A single species of this 

 type now exists in China {dmdurus cantonensis); but this is perhaps a returned emi- 

 grant from America rather than a direct oflfshoot of the parent stock. Even before 

 becoming acquainted with Professor Cope's work, "Tertiary Vertebrata, " it seemed 

 to us that the Ikujrhuc were derived from the Pimelodincr. The presence of a genus 

 of Tochisuriiue or marine Pinulodina' in the North American Tertiary deposits (Dr. 

 Cope was unable to decide which) confirmed my previous notions. The American 

 Bayritue are Pimelodinm plus a nasal barbel, the last barbel to be developed. They 

 resemble most the rimelodincv with vomerine teeth, and indeed, the genus Eliineaistts 

 possesses them. 



tSee Histoire Naturelle des Poissons, vol. 18, p. 486 (note). 



