CALIFORNIA ACADEMY OF SCIENCES. 



Doras costatm Lacepede, Hist. Nat. Poiss. v, 116, 1803 [in part] 

 (South America); Hancock Zoological Journal, iv, 242, 1828 

 (Demarara); Cuv. & Val. Hist. Nat. Poiss. xv, 268, 1840 (Gui- 

 ana); Schomburgk, Fish. Guiana, part i, 156, 1841; Castelnau, 

 Anim. Amerique du Sud. 48, 1855 (Amazon); Giiiither, Cat. 

 Fish. Brit. Mus. v, 201, 1864 (British Guiana; Eiver Cupai); 

 Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser. vol. i, 161, 1888 

 Rio Preto; Kio Puty; San Gongallo; Xingu Cascade; Obidos; 

 * Gurupa; Teffe). 



Platydoras costatus Bleeker, Nederl. Tijd. Dierkunde, i, 16, 1863 

 (name only); id. Silures de Suriname, 38, 1864 (Surinam). 



Habitat: Kio San Francisco; Parahyba; Amazon and Solimoeiis; 

 Guiana region. 



The depth under the dorsal spine little less than the 

 width; caudal peduncle about as deep as wide. Head as 

 wide as long, its depth 1| in its length; anterior profile 

 steep; opercies, suborbital, and nasal bones and entire 

 upper portion of the head with radiating series of gran- 

 ules. Dorsal plate with a narrow inward-directed pro- 

 cess behind. Anterior portion of the head flat, poste- 

 rior portion arched. Fontanel wedge-shaped. 



Eye large, 1J-2J in the snout, 3i-5i- in the head, l-J-2 

 in the interorbital. 



Maxillary barbel reaching second fourth of the pecto- 

 ral spine; postmentals little beyond base of pectoral, 

 mental about half as long as the postmental barbels. 



Snout narrowly rounded, its width at the rictus 2J in 

 the head. Upper jaw projecting. Teeth villiform, in 

 moderate bands. 



Breast entirely covered with skin. 



First and second hook-bearing lateral scutes touching 

 the dorsal plate above, lower than the third scute which 

 is 1J in the head; between the scapula and the hook- 

 bearing scutes are two granular plates; the hook-bearing 

 scutes covering the entire sides, leaving a naked dorsal 

 and ventral surface between, the scutes becoming lower 

 backward, conforming to the outline of the body, and 

 not meeting the bases of the adipose and anal fins; the 



