382 Annals of the Carnegie Museum. 



Cotypes, Nos. 26830-^, 9.2-10.5 cm., from the same place. 



D. .5 (.4 and a filament in two of the small examples); A. 9 or 

 10; V. 5; P. .5; C. 18; eye 5.5 to 6.25 in head, 1.5 to 2 in snout, less 

 than I between nares, 3.5 to 3.75 in interorbital space; depth of body 

 4.5 to 5 (4.66 in type); head 3.5 to 3.75 in length; length of dorsal 

 spine 2.5 in that of head; length of pectoral spine 1.75 in the same; 

 length of caudal peduncle from adipose to median base of caudal 1.5 

 in length of head; least depth of caudal peduncle 2.5 to 3 in length of 

 head; average thickness of caudal peduncle in its depth .7; length of 

 anal about the same as that of the ventrals; origin of anal and adipose 

 almost opposed; in the type the humeral process is four-fifths as long 

 as the pectoral spine; the fins, excepting the dorsal and caudal, are 

 colorless; some have the caudal margined with dark as in typical 

 G. albescens; some have about four rows of larger basal caudal spots, 

 which are followed by about the same number of finer spots with the 

 inner surfaces of the lobes edged with white; head and back covered 

 with larger spots, which fade into peppered sides; entire ventral surface 

 white; maxillary barbels reaching to end of, or beyond, the humeral 

 process; mental barbels not reaching more than half of the distance 

 to the bases of pectorals; cleft of mouth not extending past the anterior 

 margin of the eyes. 



This species is closely related to G. albescens, two examples of which 

 from the Rio Paranahyba (Entre Rios) in some details resemble 

 the specimens from the Iguassu, but their bodies are not so round, 

 and are more compressed posteriorly, their pectoral and dorsal spines 

 are longer, their caudal peduncle is narrower, their caudals more 

 deeply forked, and their depth less than in the examples from the 

 Iguassu. One specimen of G. albescens from Porto Alegre, Rio Grande 

 do Sul, has an even mottled color-pattern composed mostly of small 

 brown spots on the back and sides, as well as the posterior ventral 

 surface, but its total length is 14 cm., against the 13.7 cm. of the 

 type specimen from the Iguassu River, and its caudal peduncle is only 

 half as thick as deep, in contrast with five-sevenths for the various 

 specimens from the Iguassu. The Porto Alegre example also had D. 

 I. 5, but I. 4 is commoner in the case of G. albesce-hs. A small specimen 

 2.5 cm. long, from the Rio Ribeira da Iguape, is more slender and more 

 compressed posteriorly, and possesses a distinct color-pattern made up 

 of very heavy dark blotches, bands, and spots, especially over the 

 dorsal and upper half of the lateral surfaces; the rest of the body, 



