95. CH.ETOSTOMTTS. 249 



** Snout without tentacles. 

 20. Chaetostomus gymnorbynclras. 

 Ancistrus gymnorhynchus, Kner, Hypostom. p. 275. 

 D. 1/7. A. 5. 

 Head much depressed, occipital and nuchal regions without any 

 prominence ; the length of the head is one-third of the total (with- 

 out caudal). Snout broad, much depressed, granulated above, with 

 a broad soft-skinned margin in its entire circumference ; tentacles 

 none. The diameter of the eye is two-fifths of the width of the 

 interorbital Bpace. Interoperculum with thirteen or fourteen curved 

 non-flexible spines. Thorax and belly entirely naked. Dorsal fin 

 higher than long ; caudal vertically truncated. Scutes of the body 

 with minute spines, not keeled. Brownish. (Kner.) 

 Puerto Cabello. 



21. Chaetostonius nudiceps. 



Hypostomus nudiceps, Mull, ty Trosch. in Schomb. Meis. Brit. Guian. 

 in. p. 631. 



D.l/7. A. 5. 



Head much depressed, occipital and nuchal regions without any 

 prominence ; snout covered with soft skin nearly to the eyes ; tenta- 

 cles none. The pectoral spine extends beyond the base of the ventrals. 

 (M. $ T.) 



British Guiana. 



22. Chaetostonius erinaceus. 

 Hypostomus erinaceus, Cuv. 8f Val. xv. p. 510. 



D. 8. A. 3. P. 1/5. 



Body short, broad, and depressed ; extremity of the snout naked ; 

 interoperculum with a bundle of about twenty setiform spines. Scutes 

 of the body rough, not keeled. ( Val.) 



Chile. 



13. Dorsal fin nine- or ten-rayed. 

 * Snout with tentacles. 



23. Chaetostonius dolichopterus. 

 Ancistrus dolichopterus, Kner, Hypostom. p. 274. taf. 3. fig. 1. 



Head much depressed, occipital and nuchal regions without any 

 prominence ; the length of the head is somewhat more than one-third 

 of the total (without caudal). Snout broad, much depressed, covered 

 with soft skin and provided with many tentacles in males, whilst a 

 great portion of its upper surface is granulated in females, only the 

 margin bearing some tentacles. Eye of moderate size, its diameter 

 being two-fifths or one-third of the width of the interorbital space. 

 Interoperculum with from six to nine curved non-flexible spines. 



