EIGENMANN: THE PYGIDIID.E, A FAMILY OF SOUTH AMERICAN CATFISHES. 279 



///. Caudal rounded; few accessory rays; origin of ventrals one-and- 

 a-half to twice as far from snout as from caudal. 



X. Stegophilus Reinhardt. 

 jj. Gill-membranes united, free from the isthmus . . XI. Acanthopoma Liitken. 

 ii. Accessory caudal rays very numerous, the tail like that of a tadpole; base of 

 caudal very narrow; no hair-like teeth on the upper lip. 



XII. Ochmacanthus Eigenmann. 



hh. Mouth narrower, the rami of the lower teeth feeble, not transverse, not meeting in 



the middle; teeth few, slender, pointed. ( Vandelliince.) 



m. A few depressible teeth in a single series in the middle of the upper jaw; 



mandibles without teeth, or with a few excessively minute teeth on the 



ends of the rami; caudal rounded or emarginate 



XIII. Vandellia C'uvier & Valenciennes. 



XIV. Urinophilus Eigenmann. 



mm. A hand of depressible teeth in the middle of the upper jaw; a series of much 

 smaller teeth laterad of the median band; no teeth on the mandible; 



caudal forked, the upper lobe longer XV. Paravandellia Ribeiro. 



mmm. Two series of depressible teeth in the middle of the upper jaw; a single 

 series of much smaller ones laterad of the median series and a claw-like 

 tooth on the end of the maxillary 1 ' 2 of the median series; two short series 

 of teeth on the ends of the mandible; caudal subtruncate. 



XVI. Branchioica Eigenmann. 

 gg. Anal long, with fifteen to twenty-five rays, its origin in front of that of the dorsal; eyes 

 large, lateral; caudal rounded or emarginate. (Tridentince.) 

 n. Opercular and subopercular patches of spines distinct; head greatly depressed, the 

 eyes infringing on both the upper and lower surfaces of the head; mouth inferior; 

 a series of fine labial teeth and strong teeth in the jaws; gill-membranes united, 

 forming a broad free fold across the isthmus; opercle long, slender, ending in a 

 few thorns; interopercle with similar but smaller thorns. 



XVII. Tridens Eigenmann & Eigenmann. 

 nn. Opercular and subopercular patches of spines confluent; head less depressed; 

 mouth subinferior; several series of strong teeth in each jaw; gill-membrane 

 broadly united with the isthmus, without a free margin. 



XVIII. Miuroglanis Eigenmann & Eigenmann. 



Genus I. Nematogenys 13 Girard. 



Nematogenys Girard, Proc. Acad. Nat. Sci. Phila., 1854, p. 198. 



Type. — Trichomycterus inermis Guichenot. 



Origin of dorsal over or slightly in front of origin of ventrals, near middle of the 

 body; nasal barbels small; a single maxillary barbel at angle of mouth; a shorter 

 mental barbel below it; mouth wide, terminal; teeth in a broad band in each jaw; 

 gill-membranes narrowly joined to the isthmus; first pectoral ray spinous, with 



12 Possibly the premaxillary. See under the genus. 



13 vrjua, to = thread, 7^115, 17 = jaw. In allusion to the maxillary barbel. 



