ANNOTATED LIST OF THE SPECIES 163 
movable joint with the wings of the ethmoid and is free of teeth; the ectal moiety 
of the maxillary with several overlapping, claw-like teeth in a single series. The 
barbels are continuous with the end of the maxillary. 
A thin, blade-like bone covers the end of the maxillary, protecting the teeth; 
the inner, proximal end of this blade-like bone is narrowed and curved around the 
maxillary. 
Genus 63: TRIDENS Eigenmann and Eigenmann 
Tridens Eigenmann and Eigenmann, 1889, Proc. Cal. Acad. Sci., (2), I, 53; 
Higenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sei., I, 339; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 400; 
Eigenmann, 1918, Mem. Carnegie Mus., VII, 369. 
Type: Tridens melanops Eigenmann and Eigenmann 
The Brazilian-Peruvian frontiers 
Two species described from closely adjacent localities, and from few types, 
but so different as to suggest distinct genera. 
Long body form, elongated anal (twenty or more rays), its origin before that 
of the dorsal; ventrals small and nearer the end of the snout than to the base of 
the caudal; head extremely depressed; eye lateral, extending upon both dorsal 
and ventral surfaces; labial teeth fine, followed by stronger teeth in the jaws; 
gill-membranes joined to form a broad, free fold across the isthmus; two maxillary 
barbels; opercle and interopercle spinous. 
127. TRIDENS MELANOPS Eigenmann and Eigenmann 
Tridens melanops Eigenmann and Eigenmann, 1889, Proc. Cal. Acad. Sci., (2), IT, 53, I¢a; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sei., I, 339; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, III, 400; 
Eigenmann, 1918, Mem. Carnegie Mus., VII, 369, pl. xl, figs. 1 and 2. 
The Amazon near the Peruvian-Brazilian frontier 
Known only from the types, the largest 27 mm. in length. Noteworthy for 
the three trident-shaped spines of the opercle, smaller preopercular spines of 
similar form and greatly reduced barbels; coterminous anal and dorsal fins, the 
rays of the former diminishing caudally; caudal fin rounded. 
Family VIII: Astroblepidae 
Siluroidei astroblepiformes Bleeker, 1863, Nederl. Tijdsch. Dierk., I, 110. 
Siluridae proteropodes (in part) Giinther, 1864, Cat. Fish. Brit. Mus., V, 4. 
Argiudae Gill, 1872, Arrangement of Families of Fishes, 19; 
Eigenmann and Eigenmann, 1888, Amer. Nat., XXII, 647; 
Eigenmann and Eigenmann, 1890, Occ. Papers Cal. Acad. Sci., I, 347. 
Argiinae Regan, 1904, Trans. Zool. Soc. London, XVII, 307; 
Regan, 1905, Ann. Mag. Nat. Hist, (7), XV, 529-534. 
Astroblepidae Eigenmann, 1922, Mem. Carnegie Mus., [X, 50. 
