186 FISHES OF WESTERN SOUTH AMERICA 
as long as eye; mandibular ramus about as long as the premaxillary, about 4 in the 
interorbital, with about 23 teeth; snout rounded; no carinae on head or scutes; depth 
of caudal peduncle 2 in its length; dorsal spine less than the length of the head; 
caudal very deeply emarginate, the upper lobe narrow, long, and pointed, equal to 
the length of the head in the smaller, lower lobe but little longer than the snout and 
eye in the smaller, equal to the head in the larger. In the largest, 15358, the caudal 
is very obliquely emarginate, the upper lobe 1.5 in the head, the lower very little 
shorter than the head. Dorsal spotted as in the others, the caudal with cross bands, 
five of them especially prominent on the lower lobe. 
Ventrals reaching anal or a little farther; pectorals beyond middle of ventrals; 
last dorsal ray not connected with the back by a membrane. 
Sandy colored; faint cross shades or spots on head and sides; fins with alternate 
series of light and dark spots or crossbands. 
Near Ancistrus bachi (Boulenger) ; differing in somewhat narrower head, shorter 
interopercular spine, rounded snout, greater depth of body and caudal peduncle. 
Genus 76: PANAQUE Eigenmann and Eigenmann 
Panaque Kigenmann and Kigenmann, 1889, Proc. Cal. Acad. Sei., (2), I, 44, negrolineatus; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 425; 
Regan, 1904, Trans. Zool. Soc. London, XVII, 242; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 410. 
Type: Chaetostomus nigrolineatus Peters 
Peru, most of Brazil, to the Magdalena 
Teeth few and spatulate, large; interopercular spines in a large bundle, erectile. 
170. PANAQUE DENTEX (Giinther) 
Chaetostomus dentex Giinther, 1868, Proc. Zool. Soc. London, 233, Xeberos. 
Panaque dentex Eigenmann and Eigenmann, 1889, Proc. Cal. Acad. Sci., (2), II, 44; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 427; 
Regan, 1904, Trans. Zool. Soc. London, XVII, 243; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 410. 
Known from a specimen of 85 mm. length, collected by Bartlett at Xeberos, 
Peruvian Amazon 
Genus 77: MONISTIANCISTRUS Fowler 
Monistiancistrus Fowler, 1939 (1940), Proc. Acad. Nat. Sci. Phila., XCI, 236. 
Type: Monistiancistrus carachama Fowler 
Range that of the one species known 
Differing from Ancistrus chiefly in the lack of the adipose fin, reduced teeth, 
and small jaws. 
