SOUTH AMERICAN NEMATOGNATHI. 363 



I. Uppermost caudal ray spinous; vertical diameter of the eye 

 2 in the interorbital; lower lip emarginate, margined with 

 short cirri; each jaw with 8-10 teeth; no keels on occipital 

 or nuchal plates; belly with about six series of plates. (Kner 

 & Steindachner.) uracantha 311. 



II. Uppermost caudal ray not spinous. 

 m. Head without keels. 



n. Lateral keels coalescing or becoming approximate, 

 o. Lower lip very broad; teeth few, small; snout plain 

 or spotted. 



p. Pectoral conspicuously spotted or barred; spots on 

 caudal, ventral and dorsal rays and posterior half of 

 each interradial membrane of the dorsal; uppermost 

 caudal ray greatly thickened, leathery; orbital notch 

 broad; loreal region concave. stubelii 312. 



pp. Pectoral and ventral fins blackish; posterior half 

 of each interradial membrane of the dorsal dusky; 

 orbital notch narrow and deep; loreal region convex. 



spixii 313. 



ppp. All fins plain; caudal equally lobed; orbital notch 

 narrow and deep; belly with 4 series of plates; upper 

 parts with numerous blackish dots. (Bleeker.) 



typus 314. 



oo. Lower lip rather narrow, teeth large and numerous; 

 a rather broad blackish band extends from the eye for- 

 ward, a narrower one downward; base of caudal and a 

 bar parallel to its margin blackish; orbital notch nar- 

 row; snout acute; belly with 5 longitudinal series of 

 scutes. phoxocephala 315. 



nn. Lateral keels remaining separate to or nearly to the 

 caudal; head high, its sides steep; orbital notch narrow 

 and deep; lips thick, papillose; no teeth in the upper 

 jaw; interorbital flattish. anus 316. 



mm. Head with keels, at least on the occipital. 



( LORICARI ICHTH YS . ) 



q. Tip of lower caudal lobe blackish; ventrals and pectorals 



dusky. 



r. Orbit with a large angular notch, almost or quite as 

 large as the orbit; anal plate rounded in front, mar- 

 gined by 3 plates; lips broad, edged with black; teeth 

 smaller and numerous. acuta 317. 



rr. Orbital notch parabolic or more or less angular; anal 



plate attenuate in front, usually margined by 2 plates; 



lips broad, plain; teeth few, minute.- maculata 318. 



qq. Margin of caudal light; head and nape arched above; 



head less than 5 in the length. 



