THE AMERICAN TETRAGONOPTERINAE. 231 



n. Humeral spot horizontally ovate; anal rays less than 36 in all but A. 

 borcalis. 

 0. Denticles of e:^h tftoth of the iinicr series of the premaxillary ar- 

 ranged in a crescent or U-shaped line. 

 p. Depth ♦.9-2.5; .some inter])olated series of scales over the anal 

 Auscles; pedorals reaching slightly beyond origin of ventrals. 

 q. Scales 34-il. ^ ' 



r. Anill rays ^0-39^ scales 39-40. 



• 16. hiinaculatus borcalis E4j(Amann. 



rr. .Anal rays ;^-a6 (most frequently 30 or 31). 



s. No s(jiies of lateral spots 15. bimaculahis (Linne). 



t. Series of spots along rows of scales. 



17. bimaculatus paraguayensis Eigenmann. 

 qq. Scales 32-36; A. 21-38; depth in the adult 1.9-2.2. 

 M. Series of spots along the rows of scales. 

 ,. 18. bimaculatus vittatus {Co.stc]na.\i) . 



uu. Lateral band silvery; no spots along rows of scales. 



19. bimaculatus lacustris (Liitken). 

 uuu. Lateral band black; no spots along rows of scales. 



20. bimaculatus novae Eigenmann. 

 pp. Depth 2. 7-2. S3; pectorals not reaching ventrals; no interpolated 



series of scales; base of anal equal to distance between the 

 dorsals. 



V. Cheek with ^ of its width naked; two maxillary 

 teeth; snout pointed; predorsal area entirely 

 scaled, with an almost complete .scries of median 

 scales; scales above the anal with rarely more 



than 2 striae 21. janeiroensis Eigenmann. 



vv. Cheek entirely covered by the second suborbital; 



one maJfflmry tooth; snout blunt, rounded; 



scales above the anal with four or more striae. 



22. goyaccnsis Eigenmann. 



00. Teeth of the inner series of the premaxillary alike in front and 



behind, the denticles arranged in a nearly straight line; 



w. Scales 7-37 to 41-6; ma.xillary with one to three 

 teeth, extending to below origin of pupil; 

 depth 2.4; head 4; eye a little more than 3 in 

 head. A. 30-33. . . .23. orlhodus Eigenmann. 

 WW. Scales 8 (rarely 9)-37 to 39 (rarely 41)-6 or 7. 

 A. 27 or 28, rarely 29. Humeral spot blended 

 with a vertical band. 



24. polaroensis Eigenmann. 



nn. Humeral spot very conspicuous, circular or vertically elongate, pre- 



ventral area compressed, with a series of very small median scales, 



the scales bordering them with the lower (median) margin truncate, 



or two or three series of small scales; series of scales below the 



lateral line decurrent (Zygogaster). 



X. Second suborbital not in contact with the 

 preopercle below. 

 y. Anal rays 36-41. A silvery lateral band. 

 Dorsal a little behind the origin of the 

 ventrals; the anterior anal rays elongate. 

 MaxiUary extending to near the anterior 

 margin of the eye. Depth 2.4-2.8; head 

 3.5; scales 8-37 to 40-10. 



25. stilbc (Cope). 

 yy. Anal rays 33 or 34; depth 2.33. 



26. magdalenae Eigenmann and llenn. 

 XX. Second suborbital in contact with the opercle 

 below. 



