132 Bulletin 47, United States National Museum. 



Pimelodus albidus, SPIX, in Agassi/, Gen. Spec. Pise. Brasil, 19, 1829, Equatorial Brazil; immr 



preoccupied. 



Pimelodus spixii, AGASSIZ, Gen. Spec. Pise. Brasil, 19, 1829, after Spix. 

 Tachisurus spixii, EIGENMANN, S. A. Nematognathi, 88, 1890. 

 Arius arenatus, CUVIER & VALENCIENNES, xv, 106, 1840, Cayenne. 

 Arius arenatus, GUNTHER, Cat., v, 172, 1864. 

 Arius laticeps, GiJNTHEE, Cat., V, 171, 1864, British Guiana; Trinidad. 



200. TACHYSURUS MELANOPUS, (Giinther), 



Head 4. P. 10; A. 21. Palatine teeth, bluntish conical; axillary pore 

 large. Dorsal spine as long as from front of eye to gill opening ; pectoral 

 spine nearly as long; shields of head finely granular; groove of fouta- 

 nelle not quite reaching occipital process ; orbital rim of eye not free above; 

 fins all more or less blackish ; inner surface of ventral blackish. Both 

 coasts of Central America; Rio Motagua (Giinther); Panama (Steindach- 

 ner). Our specimens from Rio Ahome, on the west coast of Mexico, above 

 Mazatlan; the original specimens from the east slope of Guatemala. It is 

 possible that the Pacific Coast form may be different from the original 

 melanopus. According to Giinther, the axillary pore in melanopus is 

 nearly as large as the nostril. In our specimens the pore is much smaller 

 than the nostril, (/ueAac, black ; 7roi>f, foot or ventral fin.) 

 Arius melanopus, GUNTHER, Cat., v, 172, 1864, Rio Motagua. 



201. TACHYSURUS FtlRTHII, (Steindachner). 



Head 3i ; A. 25. Palatine teeth granular, coarser than in T. melanopus; 

 pectoral spine reaching at least halfway to middle of ventrals ; jaws sub- 

 equal ; occipital process not greatly narrowed behind ; gill rakers long 

 and slender, 4 -{- H I gill membranes united to isthmus, without free mar- 

 gin ; axillary pore small. (Eigenmann.) Panama. (For Ignatius Fiirth, 

 Austrian consul at Panama.) 



Arius furlhii, STEINDACHNER, Ich. Beitr., iv, 29, 1876, Panama. 

 Tachisurus furthii, EIGENMANN, S. A. Nematognathi, 90, 1890. 



202. TACHYSURUS VARIOLOSUS, (Cuvier and Valenciennes). 

 A. 22 or 23. Teeth on the palate granular, the patches without backward 

 projection ; no teeth on vomer ; gill membrane not forming a free margin 

 across the isthmus. Head broader than high; soft portions of the head 

 pitted ; length of head to end of occipital process little less than 3 in the 

 length, granular portion 5 longer than smooth portion of the head. Fon- 

 tanelle not continued as a groove. Maxillary barbels extending beyond 

 middle of pectorals. Cayenne. (Cuvier & Valenciennes.) (variolosus, 

 pock-marked.) 



Arius variolosus, CUVIER & VALENCIENNES, xv, 107, 1840, Cayenne. 



Arius variolosus, GUNTHER, Cat., V, 173, 1864. 



Tachisurus variolosus, EIGENMANN, S. A. Nematognathi, 92, 1890. 



203. TACHYSURUS MULTIRADIATUS, (Gunther). 



Head 4 in total length; depth 5|. D. I, 7; A. 27 (5, 22). Barbels short, 

 not reaching gill openings; teeth on palate granular, paved, in 2 small 

 bands, widely separated on median line; fontanelle long and narrow, 



