Durbin : The Expedition to British Guiana. 57 



which is continued upon the base of the caudal ; and a streak from 

 above the anterior ten anal rays to the mandible without black chroma- 

 tophores. No humeral spot ; sometimes a small dark spot at the base 

 of each caudal lobe. Teeth mostly three- to five-pointed. 



Head 3.75, depth 3.33 to 3.75; D. 11, A. 20-22 ; scales 5-31 to 

 34-3 to 3.5 ; eye 2.5 in the head ; snout |- of eye. Interorbitals less 

 than eye about 2.75 in head. 



Compressed, head at base of the occipital process f of the greatest 

 depth. Preventral region rounded, without complete regular series of 

 median scales. Postventral region narrow. Predorsal region rounded, 

 median series of scales incomplete, always more or less irregular near 

 the head. 



Occipital process from one-sixth to one-seventh of the distance from 

 its base to the dorsal, bordered by three scales. Interorbitals convex. 

 Frontal fontanel much narrower than parietal, triangular, two-thirds 

 of the parietals without the occipital groove. Second suborbital leav- 

 ing a narrow naked margin behind and below. Snout short ; mouth 

 moderately large. Lower jaw included when the mouth is closed. 

 Maxillary J of the eye. Mandible equal to the eye, 2.5 in head, 

 much weaker than the upper jaw. Naked area of cheek \ the eye in 

 width. Premaxillary with five three- to five-pointed teeth in the inner 

 row and two or three narrow tricuspid teeth in the outer row. Maxil- 

 lary with two to four, three- to five-pointed teeth. Dentary with four 

 or five, five- to seven-pointed teeth in a graduated series followed by 

 seven or eight minute tricuspid and conical teeth on the sides. 



Gillrakers 8 -f 6. 



Scales cycloid, regularly imbricate, striae few, variable in number 

 (2 to 7) ; no interpolated scales or rows of scales. Anal sheath short, 

 of three scales covering the bases of the first five anal rays. Caudal 

 scaled over the basal fourth. Lateral line with pores on six to nine 

 scales. Very slightly decurved. 



Origin of dorsal equidistant from the snout and caudal, penultimate 

 ray one-third the longest, which is 3-| into the length. Origin of the 

 anal on the vertical from the last dorsal ray. Anal deeply emarginate, 

 longest ray four-fifths as long as the base. Caudal equal to the length 

 of the head. Ventrals on the vertical from the second scale in front of 

 the dorsal. Ventrals just reaching the first or second anal rays. Pec- 

 torals reaching the first scale in front of ventrals. 



No true humeral spot ; pores and margins of the first three or four 



