356 MEMOIRS OF THE CARNEGIE MUSEUM. 



No nasal or mental barbels; lower barbel at angle of mouth minute or well 

 developed; mouth very wide, inferior; eye large, superior; posterior nares between 

 the anterior margins of the eyes; gill-opening very small; first pectoral ray not 

 spinous, not produced in a filament; accessory caudal rays very numerous, the 

 caudal greatly contracted at base; origin of anal behind that of the dorsal; teeth 

 very numerous, in regular series, none on the lip of the upper jaw. 



Key to the Species of Ochmacanthus. 

 a. Maxillary barbel reaching pectoral; origin of dorsal equidistant between tip of caudal and snout or 

 nearer caudal; accessory caudal rays highest near the middle; distance between last anal ray and 



caudal two in its distance from the snout. (Gyrinwrus) 1. batrachostoma (Bibeiro). 



aa. Maxillary barbel about as long as the eye, reaching tip of interopercular spines; origin of dorsal much 



nearer tip of caudal than snout; accessory caudal rays graduate to the caudal into which they 



gradually merge. (Ochmacanthus). 



b. Distance between last anal ray and caudal 4-4.5 in the length; origin of dorsal in advance of 



origin of anal; ventrals not reaching anal; gill-opening extending from the opercle to behind the 



middle or lower part of the opercular spines ' 2. reinhardti (Steindachner). 



bb. Distance between last anal ray and caudal three in its distance from the snout; origin of dorsal 

 over origin of anal, ventrals reaching anal; gill-openings confined to the region between the 

 interopercular and opercular spines 3. flabelliferus Eigenmann. 



1. Ochmacanthus batrachostoma (Ribeiro). (Plate LV, figs. 1-3.) 



Gyrinurus batrachostoma Ribeiro, I. c. (S. Luiz de Caceres.) 

 Habitat. — Upper Paraguay. 

 Known from the type, a specimen 32 mm. long, and 



7553, C. M., about 31 mm. Puerto Suarez, swampy shore of big bay between 

 Brazil and Bolivia. May 7, 1909. Haseman. 



7554, C. M., 30 mm. Rio Jauru, twenty-eight miles above its mouth at Campos 

 Alegre, thirty miles southwest of Caceres. June 2, 1909. Haseman. 



Head 5.5-6.5; depth 6.5-9; D. 10-12; A. 8-9; P. 4; eyes superio-lateral, three 

 or four in the head, longer than the snout, about equal to the interorbital ; maxillary 

 barbel reaching axil of pectoral, the lower one to the opercular spines; head as 

 broad as long; six to eight opercular spines arranged in a group; interopercle with 

 about five to eight spines in one or two series; teeth conical, in three parallel series; 

 body depressed in front, compressed behind; dorsal and anal rounded; dorsal 

 behind the ventrals, its origin equidistant from tip of snout and tip of caudal in the 

 figure of the type, its distance from the caudal 1.3-1.5 in its distance from the snout 

 in the specimens enumerated above; anal partly under dorsal, distance of its last 

 ray from the caudal about 3.5 in its distance from the caudal in the specimens at 

 hand; caudal minute, rounded, hidden in the accessory rays which are greatly 



