86 CALIFORMIA ACADEMY OF SCIENCES. 



Gill-membranes forming a fold across the isthmus. 

 Gill-rakers 5+11. 



Pectoral pore moderate; vertical series of pores present. 



Distance of dorsal spine from tip of snout 2|- in the 

 length; outer margin of the spine slightly granular, the 

 inner margin somewhat serrate; its length li-li in the 

 head. 



Space between dorsal and adipose fins 3J-3| in the 

 length; adipose fin shorter than the dorsal fin, its pos- 

 terior margin free. 



Caudal fin deeply forked, the upper lobe longer, some- 

 what falcate, 3^ in the length. 



Anal fin emarginate, about as long as high, the high- 

 est ray 2 in the head. 



Pectoral spine longer than the dorsal spine, its outer 

 margin roughened, its inner margin sharply serrate, its 

 length li-l| in the head. 



Plumbeous above, white below; all the fins beautifully 

 peppered with brown spots. 



Head 3|-34; depth 4J-5J; D. I, 7; A. 19-20. 



Three specimens .25 m.-.32 m. long. . Rio Doce; 

 Hartt & Copeland. 



57. Tachisurus nuchalis. 



Arius nuchalis Gtiuther, Cat. Fish. Brit. Mus. v, 171, 1864 (British 



Guiana). 

 Oaleichthys nuchalis Jordan, Proc. U. S. Nat. Mus. 1886, 559 (name 



only). 

 Tachisurus nuchalis Eigenm. & Eigenm. Proc. Cal. Acad. 2d. Ser. 



vol. i, 1888, 145 (name only). 

 Habitat: British Guiana. 



58. Tachisurus agfassizii. 



Tachisurus arjassizii Eigenm. & Eigenm. Proc. Cal. Acad. 2d Ser, 



vol. 1, 1888, 145 (Eio Grande do Sul). 

 Habitat: Eio Grande do Sul. 



Body compressed, especially backward, the depth 

 greater than the width. Head narrowed forward, its great- 

 est width 1| in its length, its greatest depth about 1\ ; width 



