THE AMERICAN TETRAGONOPTERINAE. 61 



34 '-3^. Eye 2.2-2.3; interorbital 2.2-2.66, equal to the eye or less than the 

 eye in the adult. 



Deep, compressed, ventral profile evenly curved to the anal, not as greatly 

 arched as in T. argenteus; anal basis nearly straight. Dorsal profile depressed 

 over eye; arched to the dorsal; dorsal basis oblique, straight; postdorsal part 

 of profile nearly straight. Preventral area with a median series of flat or slightly 

 keeled scales, bordered on the side by a series of angularly bent scales; post- 

 ventral area with a series of small, narrow bent scales, the area compressed; 

 predorsal region bluntly keeled, the scales not notably small, the median series 

 of eight or nine scales reaching the occipital process. 



Occipital process long, one third of the distance from its base to the dorsal, 

 bordered by three or four scales on each side; groove of the occipital fontanel 

 reaching to its tip; interorbital convex; second suborbital not covering the 

 entire cheek; maxillary equal to the distance from tip of snout to pupil; five 

 or six teeth in the front series of the premaxillary (five in thirteen cases, six in 

 fourteen), the third tooth from the middle usually withdrawn from the line; 

 five teeth in the inner series of the premaxillary; usually three teeth (two in 

 five cases, three in eighteen, four in four) on the maxillary; lower jaw with 

 four large graduated teeth and many small ones on the side. 



Gill-rakers about 4 + 13, the longest about one third the diameter of the 

 eye. 



Scales deeply imbricate, striae lacking or an occasional line on the scales, 

 the striae fairly numerous near the caudal; scales of the sides continuous with 

 the anal sheath which is composed of three series of scales near its anterior end, 

 becoming reduced to a single series on the last rays; caudal lobes densely scaled 

 to near their tips in the adult, the scales much more readily caducous than those 

 of the sides; lateral line obliquely descending on the first seven scales then 

 nearly straight. A well-developed axillary scale. 



Origin of dorsal equidistant from tip of snout and tip of adipose or caudal, 

 its highest ray three to four times as high as its lowest, two to three in the length; 

 anal in the adult with its margin nearly straight; the anterior rays being but 

 slightly prolonged; origin of ventrals equidistant from the tip of snout with 

 the dorsal and equidistant between the tip of snout and end of anal, reaching 

 to anus; pectorals usually falling short of the ventral, except in Guiana speci- 

 mens. 



1 Of ten specimens from Lagoa Pereira one has twenty-nine, three have thirty, four thirty-one, and 

 two thirty-two. Of ten specimens from Roekstone one lias thirty-one, three have thirty-two, five thirty- 

 three and one has thirty-four. 



