250 Fretp Museum or Natura. History — Zodérocy, Vor. X. 
Of this species 62 specimens, ranging from 30 to 260 mm. in length, 
were preserved. It is common in the Rio Tuyra Basin, but only a few 
specimens were obtained in the Rio Bayano and a single specimen in the 
Rio Chagres. The last was speared at night by torch light by a native 
at Alhajuela. 
This species lives among the rocks, apparently prefering the rapid 
courses of streams. In clear water it may often be seen huddled close 
to the rocks to which it is able to attach itself by means of its sucking 
mouth and flat ventral surface. It feeds on alge and other plants. Its 
alimentary canal is convoluted and many times the length of the body. 
It is prepared as food by the natives of Darien, by boiling it in water. 
Habitat: Both slopes of Panama. 
8. Genus Ancistrus Kner. 
Ancisirus Kner, Denkschr. K. Ak. Wiss. Wien, VII, 1853, 272 (sp.); 
Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 77 (type Hypostomus 
cirrhosus Cuvier & Valenciennes). 
Thysanocara Regan, Ann. & Mag. Nat. Hist., Ser. 7, XVII, 1906, 95 
(type Hypostomus cirrhosus Cuvier & Valenciennes). ' 
Body anteriorly broad; caudal peduncle posteriorly compressed; 
margin of snout naked, bearing tentacles; the naked margin broad in 
males and with many tentacles, narrow in the females and with few 
short tentacles; preopercle independently movable, bearing spines; the 
premaxillaries and dentaries of about equal length, the mandibular 
ramus much narrower than interorbital; plates on head and scutes on 
body without prominent ridges or carinations; adipose fin well developed. 
KEY TO THE SPECIES. 
a. Fins moderately elevated, the posterior rays of the dorsal failing 
to reach adipose when deflexed; base of dorsal scarcely equal to 
the distance from the base of the last ray to the tip of the spine of 
the adipose; pectoral fins failing to reach the middle of the 
ventrals, the spine notably shorter than the head; second scute 
behind occipital without a distinct median suture. 
chagrest, p. 251. 
aa. Fins strongly elevated, the posterior rays of dorsal reaching past 
origin of adipose when deflexed; base of dorsal equal to the 
distance from the base of the last ray to the base of caudal; 
pectoral fins reaching to or past the middle of ventrals, the spine 
longer than head; second scute behind occipital with an evident 
median suture. SPINOSUS SP. NOV., P. 252. 
