1]2 OSTAEIOPHTSI. 



Supraoocipital with a median ridge and bordered posteriorly by a single scute. Dark spots on head, 

 body, and fins. 



Hah. Panama to Paraguay. 



This species, which attains a length of 350 mm., is known to range from Venezuela 

 to Paraguay. It has also been recorded by Kner and Steindachuer (Abhandl. 

 Bayer. Akad. x. 1865, p. CO) from Panama. The Panama specimens are said to 

 differ from the typical P. guacari in having more numerous teeth (40 on each side), a 

 lower occipital keel, &c., but the probable explanation is that Kner and Steindachuer 

 had examples of the true P. guacari and compared them with specimens of P. verves, 

 Cuv. & Val., a species which has not usually been distinguished from P. guacari, but 

 which differs from it in the fewer teeth, higher occipital keel, &c. 



2. ANCISTRUS, Kner. 



Ancistrus,G\\\, Ann. Lye. N.York, vi. 1858, p. 407; Regan, Trans. Zool. Soc. xvii. 1904, p. 221. 



Similar to Plecostoimis, but operculum and interoperculum independently movable, the latter usually with a 

 group of spines or bristles which can be everted. 



Thirty-one species from Tropical America. 



1. Ancistms aspidolepis, Giinth. 



Ancistrus aspidolepis, Regan, Trans. Zool. Soc. xvii. 1904, p. 230. 



Dorsal I 7. Anal I 4. Scutes all strongly keeled, 25 in a longitudinal series. Interoperculum armed with 

 a few short spines. Small dark spots or vermiculations on head, body, and fins. 



Tlalj. Panama, Veragua. 

 Total length 280 mm. 



'O' 



.3. CH^TOSTOMUS, Tschudi. 

 Ch(ctostomus, Regan, Trans. Zool. Soc. xvii. 1904, p. 241. 



Similar to Ancisfi-iis, but the snout with a naked margin. 



Fifteen species, chiefly from the Andes of Peru, Ecuador, and Colombia, but extending 

 into Venezuela and Panama. 



1. Chsetostomus fischeri, Steind. 



dhcetostomus fischeri, Steind. Denkschr. Ak. Wien, xli. 1879, p. 164, t. 4. fig. 9. 



Dorsal I 8. Anal I 5. 23 to 24 scutes in a longitudinal series, none of them keeled. Interoperculum armed 

 with 1 or 2 short spines. Head and anterior part of body with little yellowish spots ; fins spotted or 

 clouded with blackish. 



Ilab. Panama, Eio Mamoni. 

 Total length 275 mm. 



