246 Fretp Museum or Naturat History — Zoétocy, Vor. X. 
We have at hand for comparison a few large male specimens from the 
Rio San Juan, Colombia. With these our specimens seem to agree in 
all characters of specific importance. 
Habitat: Rio Tuyra Basin, Panama, and south to Ecuador. 
Family II. Loricariidz. 
Sides and back and sometimes the lower surface covered with bony 
plates, these often provided with teeth-like spines; mouth wholly infe- 
rior, provided with reflected, disk-like lips; premaxillaries not pro- 
tractile; maxillary bone thin, bearing a barbel which is partly united 
with the oval disk; no mental or nasal barbels; teeth if present hooked 
and in a single series; no teeth on palatines; no frontal or occipital 
fontanel; nostrils close together; gill-membranes broadly joined to the 
isthmus; dorsal fin present, situated on the abdominal portion of the 
spinal column and not connected with the occipital by processes; 
adipose fin, if present, composed of a spine and a membrane; anal fin 
usually present, short; alimentary canal very long, coiled. 
MEASUREMENTS. 
In the present work the length of head in this family is measured 
to the margin of the temporal plates which usually extend to above 
base of pectorals; the total length of body is measured to tip of longest 
ray of caudal, exclusive of filament, if present; the standard length as 
usual is measured to base of caudal fin; by the mandibular ramii are 
meant the two bones bearing teeth, forming the posterior border of the 
mouth and corresponding to the lower jaw in other fishes. 
KEY TO THE GENERA, 
a. Body rather short, robust; caudal peduncle short, compressed; 
adipose fin usually present. 
b. Adipose and anal fins present. 
c. Scutes on back and sides distinctly carinate; opercle firmly 
attached to the interopercle and not independently movable. 
Plecostomus, p. 247 
cc. Scutes on back and sides without prominent ridges or carinations; 
opercle more or less freely movable. 
Margin of snout naked, with or without tentacles. 
e. Snout without tentacles; mandibular ramus about equal to 
interorbital. Chetostomus, p. 249. 
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