214 MEMOIRS OF THE CARNEGIE MUSEUM 



snout; upper jaw with three series of teeth; teeth of the two outer series conical, those 

 of the inner series broad, removed from the others, forming a solid palisade; no labial 

 teeth; lower jaw with an outer series of long, curved, claw-like teeth in the lip, 

 and four series in the jaw, of which the first is short, near the middle, the second 

 extends farther to the sides, the third is longest, extending from the middle to the 

 side of the jaw, the fourth is shorter again and confined to the sides, not reaching 

 the median line of the jaw. Preopercle with nine claw-like erectile spines; opercle 

 somewhat prolonged, earning a bunch of nine spines similar to those of the pre- 

 opercle above and behind the gill-opening. Gill-opening small, entirely above the 

 level of the middle of the pectoral; outer maxillary barbel about as long as the 

 eye, the inner one minute. 



Pectorals partly adnate; ventrals small, free, reaching anal; dorsal about equal 

 to the anal and but slightly farther forward. 



Light, with numerous chromatophores more or less aggregated in places; a 

 black spot on base of caudal. 



Family VII. CALLICHTHYID.E. 



= Callichthyoidei Bleeker, Nederl. Tijdschr. Dierk., I, 1863, 82. 



< Siluridce proteropodes Gunther, Catalogue, V, 1864, 4 (Hypostomatince in part.) 



= Callichthyidce Gill, Arrangement of the Families of Fishes, 1872, 19. — Eigen- 



mann and Eigenmann, Occasional Papers Cal. Acad. Sci., I, 1890, 449. 



Distinguished from all other fishes by the double series of dermal plates meeting 

 along the middle of the sides. A small homogeneous group, confined to South 

 American waters. 



Key to the Guiana Genera of Callichthyidje. 



a. Two pairs of nuchal plates between occiput and dorsal plate; suture between humeral and coracoid 



processes extending almost horizontally to the posterior margin of the pectoral armature; a 



large opening between coracoid and clavicle below and in front of the pectoral spine. 



b. Coracoid covered with skin. Sides of the head without bristles; no mental barbels; lower jaw 



with small bands of teeth on the sides; a naked area along dorsal and ventral surfaces; 



suborbital bones concealed; dorsal spine rudimentary; caudal rounded Callichthys. 



bb. Coracoid exposed below; coracoid bone joined to the clavicle for its whole length. Two barbels at 



each rictus, none at the symphysis. Lower lip without barbels; a naked area along ventral 



surface; caudal rounded or emarginate; dorsal spine low and flat; pectoral spine serrate on 



inner margin in the young, outer margin and surfaces covered with bristles. . . Hoplosternum. 



aa. Occipital with a narrow process extending to the dorsal plate. D. 1,6-8; coracoid process exposed; 



suture between coracoid and humeral processes extending from the large pectoral pore obliquely 



downward and backward to the ventral margin of the pectoral armature; dorsal and pectoral 



spines long, pungent, their outer surfaces smooth Corydoras. 



