46 



D. 1, 61; A. 151 (4.111); C. 23, 7.12. 11; P. 1. 10; V. 1.8. 

 The color above is olivaceous brown, and beneath light. The fins 

 are not margined with darker. 



One specimen was caught by Dr. Suckley in the Platte River. 



Synopsis of the genera of the sub-family of Pimelodin^. 

 By Theodore Gill. 

 The following synopsis of the genera of the sub-family of Pimelo- 

 dince was drawn up to assist in the better appreciation of their 

 characters, and their relation to each other, when engaged in the 

 preparation of the Report on the Ichthyology of the route pursued by 

 Captain J. H. Simpson. In the forthcoming Report of that gentle- 

 man, the nomenclature of the North American genera, and the 

 reasons that have induced us to change the application of the ancient 

 name of Pimelodus, are fully discussed. 



Sub-family Pimelodin.e Gill. 



Body stout or moderately elongated. Head short or oblong, de- 

 pressed or sub-compressed, covered by a more or less thick skin, and 

 without a casque. Eyes subcentral, various in size according to genus. 



Barbels six or eight ; two supramaxillary and four inframaxillary ; 

 when eight are present, there is a pair of nasal barbels. 



Teeth on both jaws, villiform or acute, and pluriserial, arranged in 

 entire or bipartite bands ; none on the vomer or palate. 



Dorsal fm subquadrate, anterior almost always with a short or 

 moderate spinous or cartilaginous ray. Adipose fin distinct, rarely 

 united with the recurrent rays of the caudal fin.* Pectoral fins, with 

 the first ray spinous and comparatively short. 



Yentral fins inserted behind the vertical of the dorsal fin. 



Lateral line straight and simple, or undivided. 



The sub-family of Pimelodinae, as thus restricted, is quite a natural 

 group, which is peculiar to the continents of North and South Amer- 

 ica, the southern and eastern parts of Asia, and the islands of the 

 Sunda-Moluccan Archipelago. All of its species are confined to the 

 fresh water of those countries. 



The difference between this and the other sub-families of Siluroids 

 relates chiefly to the form and the position of the dorsal fins. It re- 

 sembles most of the allied sub-families in this respect, but from all of 

 them it differs by characters, which, although not in themselves 

 very important, are of considerable value from their permanency, and 

 the difference of habit with which they are coincident. 



The nearest allies are the Hemipimelodinae, of Avhich at present 

 only one genus is certainly known. The fishes of that sub-family are 

 distinguished from those of the present one by a well-defined granu- 



* The geuus Xotunis of Kalinesque is the ouly one so distiuguished. 



