198 SILURID^. 



2. Centromochlus aulopygius. 

 Kner, I, c. p. 432. fig. 25. 



D. ±. A. 9-10. P. 1/4. 



4-5 ' 



Head and neck granulated above ; eye of moderate size, one-fourth 

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

 of the pectoral spine. Dorsal spine serrated in front, smooth behind, 

 shorter than that of the pectoral fin, which is as long as the head. 

 Caudal deeply emarginate. Back and sides brown ; dorsal and caudal 

 fins with blackish or whitish spots and dots. 



Rio Guapore ; Essequibo. 



a-e. Five inches long. Essequibo. From Mr. Ehrhardt's Collection. 



77. TRACHELYOPTERUS. 



Trachelyopterus, Out. 8f Val. xv. p. 220. 



Trachelyopterus et Trachelyopterichthys, Bleek. Nederl. Tydschr. 

 Dierk. 1863, p. 111. 



Adipose fin none ; dorsal fin short, with a pungent spine and with 

 four or five soft rays ; anal fin long. The upper surface of the head 

 osseous. Barbels six. Teeth villiform, none on the palate. The 

 gill-opening does not extend downwards beyond the root of the pec- 

 toral. 



South America. 



a. Ventral smallish, with six rays : Trachelyopterus, Blkr. 



1. Trachelyopterus coriaceus. 

 Guv. $ Val, xv. p. 221. pi. 438. 



B. 6. D. 1/5. A. 32. P. 1/7. 



Head and neck granulated above ; the length of the head is rather 

 more than one-fourth of the total (without caudal) ; the lower jaw 

 is the longer. The maxillary barbel extends to the origin of the 

 dorsal ; humeral process short. Dorsal spine rather feeble ; pectoral 

 spine strong, not serrated along its outer margin. Caudal rounded. 

 (Val.) 



Cayenne. 



/3. Ventral large, with sixteen rays : Trachelyopterichthys, Blkr. 



2. Trachelyopterus taniatus. 

 Kner, Sitzgsber. Wien. Acad. 1858, xxvi. p. 434. fig. 26. 



D. 1/4. A. 51. P. 1/6. 



Head and neck granulated above ; the length of the head is nearly 

 one-sixth of the total (without caudal) ; the lower jaw is the longer. 

 The maxillary barbels extend beyond the base of the pectorals ; 

 humeral process long. Dorsal spine granulated, of moderate strength, 

 half as long as the head ; pectoral spine longer than the head, com- 



