95. CBLETOSTOMTJS. 241 



II. Snout more or less naKed. 



a. Dorsal fin eight-rayed : Ancistrus, sp., Blkr. 



* Snout with tentacles, p. 247. 



** Snout without tentacles, p. 249. 

 fi. Dorsal fin nine- or ten-rayed. 



* Snout with tentacles, p. 249. 



** Snout without tentacles; upper lahial fold not dilated in the 

 middle, p. 250. 

 *** Snout without tentacles; upper labial fold much dilated in the 

 middle : Chcetostomus, Heck., p. 250. 



I. Margin of the snout with hard granulations. 

 a. Dorsal fin nine-rayed. 



1. Chaetostomus serratus. 



Hypostomus serratus, Cuv. fy Vol. xv. p. 503. 

 Pseudacanthicus serratus, Meek. I. c. p. 79. 



D. 1/8. A. 6. P. 1/6. V. 1/5. 



Head large, depressed, longer than broad, its length being one- 

 third of the total (without caudal) ; snout broad and elongate ; inter- 

 orbital space flat ; eye rather small. The margin of the snout is 

 covered with small spinous plates, the spines on the side of the snout 

 being the largest ; interoperculum with a bundle of about fifteen 

 slender spines, which are much longer than the orbit, but do not 

 extend beyond the gill-opening. Thorax and belly naked. Dorsal 

 fin sometimes a little higher than long, sometimes lower, the length 

 of its base being rather less than its distance from the caudal ; there 

 are eight scutes between the two dorsal fins. Lower caudal lobe not 

 much longer than upper. Pectoral spine strong, covered with long 

 hook-like spines, and extending somewhat beyond the base of the 

 ventral. Ten scutes between anal and caudal. Scutes of the body 

 covered with spines, those along the median line of each scute being 

 long, similar to those of the pectoral spine. Posthumeral ridge in- 

 distinct. Deep black or brownish black, with a few inconspicuous 

 small round whitish spots on the lower part of the tail. 



Surinam. 

 a-b. From twelve to fifteen inches long. From the Stuttgart Museum. 



2. Chgetostomus spinosus. 



Hypostomus spinosus, Casteln. Anim. Amer. Sud, Poiss. p. 45. pi. 22. 

 fig. 3. 



D. 1/8. A. 6. 



Snout depressed and rather long ; body somewhat elongate ; eye 

 small. Head, scutes of the body, and the outer fin-rays covered with 

 spines. The pectoral spine is not longer than the head. All parts 

 covered with small round black spots. (Cast.) 



River Amazons. 



Kner considers this fish identical with Acanthicus hustrix, Spix 

 (Wiegm. Arch. 1858, p. 348). 



VOL. V. K 



