266 CALIFORNIA ACADEMY OF SCIENCES. 



XLVII. CENTROMOCHLUS. 



Centromochlus Kner, SB. Ak. Wien, xxvi, 430, 1857 

 (megalops =keckelii). 



Glanidium (Reinhardt MS.), Liitken Dan. Vid. Selsk. 

 31, 1874 (albescens). 



Type: Centromochlus megalops Kner. 



Barbels six, those on the mandible short and dis- 

 posed as two pairs. Palatine teeth none; vomer occa- 

 sionally with teeth. Eyes very variable in size, covered 

 with skin. Adipose fin very short. Dorsal fin of a 

 spine and 4 or 5 rays. Anal short. Ventrals inserted 

 posterior to the dorsal, with 6 rays. Humeral process 

 present. Occipital process firmly joined to the dorsal 

 plate. Bones of the head naked, granular except in 

 albescens. Gill-membranes confluent with the skin of 

 the isthmus. 



Habitat: Streams from Rio Janeiro to Canelos and 

 Guiana. 



We here consider Glanidium as a subgenus of Centro- 

 mochlus. In cases like this where characters are of 

 doubtful value it must remain merely an opinion 

 whether the form under consideration is a genus or sub- 

 genus. 



DOUBTFUL SPECIES OF CENTROMOCHLUS. 



205.1. Arius oncina Schomburgk, Fishes of Guiana, 

 part i, 173, pi. iv, 1841 (Rio Padauiri). 



ANALYSIS OF THE SPECIES OF CENTROMOCHLUS. 



. Head granular above. (CENTROMOCHLUS). 



6. Eye very large, directed downward more than upward. Pectoral spine 

 long, reaching the ventrals. heckelii, 206. 



bb. Eye moderate or small, lateral. 

 c. Body plain or with light spots. 



d. A. 7; eye 4 in the head; maxillary barbels nearly coterminous 

 with the pectoral fins. Dorsal plate with its process extending 

 inward behind. Height of the dorsal not much less than the 

 length of the head; the spine obsoletely serrate behind. Pectoral 



