314 CALIFORNIA ACADEMY OF SCIENCES. 



Hypophthalmufi fimhriatus Kiier, 1. c. 444, plate 9, fig. 30 (Rio Negro); 



Gtluther, 1. c. (copied). 

 H ypophthalmns perporosus Cope, 1. c. (Naiita); Steiudachuer, Fluss- 



fische Siidamerika's, iv, 4, 1882 (Eio Hiaallaga; Eio Amazonas). 

 Habitat: Amazous and tributaries, and northward. 



The species of HypopJdhahniis are based chiefly on the 

 variation of the barbels and the lateral pores. • We have 

 examined specimens from .12-. 40 m. long. Some agree 

 with one of the above quoted descriptions, and some 

 with another. They are labeled eAentatus, Jimbriatus , 

 and longijilis. There is little doubt but that the species 

 have been based on the different stages of one species, 

 as we shall endeavor to prove. 



Steindachner had two specimens of i^erporosufi, one 

 of which had the pores of the lateral line and its branches 

 much less evident than the other. 



In some of the specimens examined by us the pores 

 are not evident on a superficial examination, while in 

 others they are so conspicuous as to attract the attention 

 at once, and in the smallest specimen there are no pores 

 except along the lateral line and at end of its very short 

 branches. 



The barbels in some appear filiform, but a closer in- 

 spection proves that all are margined more or less 

 broadly. The smallest specimen has the membrane of 

 the barbels very broad near the base; the maxillary bar- 

 bel extends beyond tip of dorsal; mental and postmental 

 barbels to the tip of the dorsal. 



In a specimen .18 m. long the maxillary barbels reach 

 the tip of the dorsal fin and the mental barbels extend to 

 the anal fin. 



In a specimen .40 m. long the maxillary and mental 

 barbels reach the base of the pectoral, while Professor 

 Cope says the specimen of .50 m. had the maxillary bar- 

 bels extending past the base of the ventral fin and the 

 mental barbels nearly to the opercular border. 



