76. CENTROMOCULUS. 197 



as long as the head ; the humeral process extends backwards to the 

 posterior third of the pectoral spine. Dorsal spine smooth in front, 

 shorter than that of the pectoral fin ; the latter is strongly serrated 

 along both edges, shorter than the head, and two-ninths or one-fifth 

 of the total length (without caudal). Caudal fin obliquely truncated. 

 Brown, with dark-brown spots. 

 Guiana ; Brazil. 



a. Half-grown. British Guiana. Purchased of Mr. Leadbeater. 



b. Adult. Guiana. Purchased of Mr. Scrivener. 



9. Auchenipterus robustus. 

 D. 1/6. A. 28. P. 1/7. V. 6. 



The bones of the head and neck are coarsely granulated ; groove 

 between the frontals short, ovate, surrounded by bone. The lower 

 jaw is the longer ; the maxillary barbels extend to the end of the 

 pectoral ; the anterior chin-barbels not quite half as long as the head. 

 The humeral process extends backwards to the posterior third of the 

 pectoral spine. Dorsal spine much more feeble and shorter than 

 that of the pectoral fin, slightly crenulated in front ; pectoral spine 

 strongly serrated along both edges, as long as the head, and one-fiftl 

 of the total length (without caudal) ; ventral and anal fins with fleshy 

 base ; caudal obliquely truncated. No granulated plate on the side 

 of the belly. Uniform dark brown. 



Demerara. 



a. Nine inches long. Purchased of Mr. Scrivener. 



76. CENTROMOCHLUS. 



Uentromochlus, Kner, Sitzgsber. Wien. Acad. 1858, xxvi. p. 430. 



Adipose fin very short ; dorsal fin short, with a pungent spine and 

 with four or five soft rays ; anal fin very short. Barbels six, cylin- 

 drical, those at the mandible short, and disposed as an anterior and 

 as a posterior pair. Teeth villiforni, none on the palate. The gill- 

 opening does not extend downwards beyond the root of the pectoral. 

 Ventrals with six rays, inserted behind the dorsal. 



South America. Small Siluroids. 



1 . Centromochlus heckelii. 



Auchenipterus heckelii, Filijypi, Guer. Rev. et Mag. Zool. 1853, p. 166. 

 Centromochlus megalops, Kner, I. c. fig. 24. 



D. 1/5. A. 7. P. 1/6. 



Head and neck granulated above ; eye very large, one-third of 

 the length of the head ; the maxillary barbels reach to the middle 

 of the pectoral spine. Dorsal spine serrated behind, rather longer 

 than the head, but shorter than that of the pectoral fin, which is 

 nearly one-third of the total length. Caudal fin deeply forked. 

 Coloration uniform. 



Bogota ; Rio Napo. 



