398 CALIFORNIA ACADEMY OF SCIENCES. 



i. Lat. 1. 28; eye 4| in the snout, 8 in the head, 3 in the in- 



terorbital; outer caudal rays little produced; middle caudal 



rays H~l| in the head. Base of the dorsal fin equal to its 



distance from the caudal, or very little less. limosus 347. 



;/. Lat. 1. 30. Eye 3 in the snout, 6-6 in the head; base of 



the dorsal equal to its distance from the posterior margin 



of adipose fin. carinatus 348. 



ee. Tip of snout granular, occasionally naked in plecostomus . 



j. Lateral plates all more or less strongly keeled; nuchal plates 



conspicuously bicarinate; shortest caudal rays 1| in the head. 



Light brown, everywhere spotted with darker. Lat. 1. 26. 



plecostomus 349. 

 jj. Lateral plates scarcely if at all keeled. Lat. 1. 27-28. 



k. Head with vermiculating light and dark lines; ventral sur- 

 face with short curved bars; occipital plate margined by 

 three nuchal plates; superciliary edge raised. 



vaillanti 350. 



kk. Head with round spots; ventral surface plain; superciliary 

 edge scarcely raised; base of the dorsal less than its dis- 

 tance from the adipose fin. villarsii 351. 

 bb. Belly partially or entirely naked.* 



o. Belly covered with minute scutes, except a quadrate space between 

 the ventrals. biseriatus 353. 



oo. Belly with scutes only on the sides, and sometimes a narrow strip 

 between the ventrals. 



p. Lat. 1. 27. Upper lateral plates with a strong median keel; head 

 with a strong occipital keel and smaller temporal keels; nuchal 

 plates bicarinate; a band between the pectorals, sides of the belly 

 and a narrow band between the ventrals covered with scutes; dor- 

 sal surface, sides and fins spotted with brown; ventral surface 

 plain. seminudus 354. 



pp. Lat. 1. 30; lateral plates not keeled. annce 355. 



ooo. Belly entirely naked. pantherinus 356. 



aa. Head without distinct ridges or keels; snout broad, rounded. 

 q. Belly entirely covered with granular plates. 

 r. Tip of snout naked. 



s. Dorsal crossed by six or seven black zig-zag stripes; base of the 

 dorsal less than its distance from the adipose; 17 scutes between 

 the anal and the caudal. Lat. 1. 30. Brownish black with black 

 dots, largest on belly; rays of the caudal, pectoral and ventral fins 

 crossed by a number of black streaks. cordovce 357. 



88. Dorsal spotted or uniform dusky; base of the dorsal longer than 

 its distance from the adipose fin. Lat. 1. 26-27; occipital bordered 

 by a single plate. 



*352 virescens Cope, should probably be placed here. 



