THE AMERICAN TETRAGONOPTERINAE. 267 



Much compressed, subrhomboidal, the dorsal profile being equally arched 

 with the ventral, the anal basis being nearly parallel with the predorsal profile ; 

 profile slightly concave over the eye, nape not sharply convex as in Tetragonop- 

 terus. Preventral very narrowly rounded, with a nearly complete median series 

 of scales; postventral area still more compressed without a median series of 

 scales. Predorsal area keeled, with but a few median scales near the dorsal, 

 then with the margins of the scales bent over the back and then naked toward 

 the occipital process. 



Occipital process narrow, nearly ^ of the distance from its base to the 

 dorsal, bordered by 3 or 4 scales. Interorbital smooth and distinctly convex. 

 Frontal fontanel extending to over the anterior margin of the pupil, not much 

 shorter than the parietal without the occipital groove. Second suborbital leav- 

 ing but a very narrow naked area behind, in contact with the preopercle below, 

 sometimes a naked angle below the sutm-e between the first and second sub- 

 orbitals. Mouth moderate. The slender maxillary not quite equal to the 

 eye in length, not extending much, if any, beyond the origin of eye. Premaxillary 

 with fom', rarely five, teeth in the outer row and five in the inner; inner surface 

 of the inner teeth convex, the points being arranged in a curved line, the middle 

 point distinctly largest. Maxillary with one small tooth. Dentary with 

 four large, graduate teeth followed on the sides by abruptly smaller teeth. 



Scales cyclbid, with numerous striae, those of the back and above the 

 pectorals regularly imbricate, those below the lateral line and beyond the pec- 

 toral with interpolated rows; in the type the first interpolated row is under 

 the 12th scale of the lateral hne and begins in the sixth series below the line; 

 the second begins dnectly under the 16th scale; another under the 4th scale 

 below the 17th scale of the lateral Une, another under the second scale below 

 the 19th of the lateral line, immediately under the 21st scale and others under 

 the fifth scale below the 22d and 23rd scales of the lateral Une ; another immedi- 

 ately under the 24th scale, another below the sixth scale under the 25th of the 

 lateral line, two others below the 2d scale under the 26th and 27th scales respec- 

 tively, and the last immediately under the 28th, which extends obliquely back, 

 reaching the posterior margin of the anal fin; axillary scale well developed; 

 anterior part of anal sheath not distinctly demarked from the scales of the 

 sides, low, of about 3 series scales in front, of one series behind. Lateral line 

 but little decurved. 



Dorsal over the 11th scale of the lateral line, origin of ventrals under the 

 9th; dorsal sharply pointed, the second and third rays sometimes slightly pro- 



