246 FIELD MUSEUM OF NATURAL HISTORY ZOSLOGY, VOL. 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. Loricariidae. 



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 of less freely movable. 



d. Margin of snout naked, with or without tentacles. 



e. Snout without tentacles; mandibular ramus about equal to 

 interorbital. Chcetostomus, p. 249. 



