512 PROCEEDINGS OF THE ACADEMY OF [Sept., 



overshot with dull silvery reflections. Head dark olivaceous-brown 

 like back, this color including all of upper lip and snout. Maxillary 

 and mandible rather grayish. Sides of head and below whitish, 

 former silvery and opercle with some golden reflections. Almost 

 all of side of head with minute brownish dots, which a little enlarged 

 and quite distinct on postorbital. Iris grayish-dusky, with silvery 

 reflections. On side of body a broad underlaid plumbeous streak, 

 ill defined and less in width than eye-diameter, extends from shoulder 

 to caudal base. In third to fifth scales of its course a nebulous 

 dusky blotch a little less than eye, and followed by a similar one 

 at eighth and ninth scales. At end of plumbeous band a large 

 dusky to blackish blotch, and this reflected out on median caudal 

 rays to their tips. Dorsal dark gray. Caudal lobes grayish basally, 

 becoming brownish distally. Paired fins and anal grayish, latter 

 with membranes dull dusky on outer portions. Pectoral and ventral 

 also slightly darker on outer portions. Adipose fin brownish. 

 Inside gill-opening with some minute dusky dots, otherwise pale. 

 Peritoneum silvery below. 



Length 3}| inches. 



Type, No. 17. Collection of S. N. Rhoads. Affluent of the Chimbo 

 River, near Bucay, Province of Guayas, Ecuador. July, 1911. 



Also Nos. 18 to 30, paratypes, same data. Head 3f to 3| ; depth 

 2f to 3^; D. in, 9; A. usually iv, 27, i, frequently iv, 25, i, iv, 26, i, 

 iv, 28, i, or iv, 29, i; scales in 1. 1. usually 35, frequently 36 or 

 37, sometimes 38, seldom 34 + usually 4, sometimes 3; usually 

 7 scales above 1. 1. to dorsal origin, frequently 8; 6 scales below 1. 1. 

 to ventral origin; usually 7 scales below 1. 1. to anal origin, frequently 

 8, seldom 6; usually 15 predorsal scales, often 16 or 17; snout 3f 

 to 4£ in head measured from upper jaw tip; eye 2f to 3^; maxillary 

 2\ to 2f ; mandible 2^ to 2f ; interorbital 2| to 3; pectoral If to 

 lj; ventral If to 2; length If to 3| inches. Small examples are 

 usually more elongate, paler or more silvery, and have the mandible 

 slightly protruding. They show the maxillary teeth, however. 



This species appears related to Astyanax simus (Boulenger), 6 

 a species originally confused with A. mexicanus (Philippi), as Tetra- 

 gonopterus petenensis, by Gimther. It differs in the size of head 

 and depth of the body. Boulenger gives the former as 3f to 4 and 

 the latter as 3 to 3|. If this refers to the total length, my examples 



6 Tetragonopterus simus Boulenger, Boll. Mus. Z. Anal. Comp. Torino, XIII, 

 No. 329, 1898, p. 2. Valley of Chota, north of Ecuador. 



