1903.] NATURAL SCIENCES OF PHILADELPHIA. 509 



crably wider than in front of the eye. and along the upper part of the 

 cheek and opercle, where it is still wider and much less intensely black, 

 merging into the color of the body and top of head. Body unspotted, 

 dark above, lighter below. 

 39. Psectrogaster curviventris sp. nov. Blanquillo. 



Type Xo. 9,919, ISO mm. (.36). Asuncion. Rio Paraguay. 



Co-type Xo. 9,918, 195 mm. (.36). Asuncion, Rio Paraguay. 



Co-type Xo. 9,920, 183 mm. (83). Asuncion, Rio Paraguay. 



Co-types X'o. 9,921, 3 specimens, 107-122 mm. (34). Asuncion, Rio 

 Paraguay. 



Co-types Xos. 9,936-9,937, 2 specimens, 145 and 160 mm. (145, 234). 

 Fuerte Olympo, Rio Paraguay. 



This species is closely related to Psectrogaster rhomhoicles . from which 

 it differs in a nmnber of characters, notably the ventral outline, the 

 number of fin raj's and scales. 



Head 3§-3i (3^ in smallest specimen) ; depth 2-2| (2i-h2f in rhom- 

 hoicles); D. 10 or 11 (12 or 13 in rhomhoicles); A. 9 or 10 (10 or 11 in 

 rhomhoicles); Lat. 1., 48-52 (53-58). 



Compressed and deep, the depth usually 2 in the length, rarely less, 

 2| in Xo. 9,937. Ventral outline regularly arched, without an angle 

 at the origin of the ventral; dorsal outline less regularly arched, the 

 base of the dorsal oblique ; the region between dorsal and nape strongl}^ 

 arched, top of head depressed. 



A narrow adipose lid in front and behind. Eye 3^-3-^-. equal to the 

 snout and anterior adipose lid, 2 in interorbital. 



Scales on back small, becoming larger on the sides and largest on 

 breast. Scales all ctenoid, becoming pectinate on breast. 



Air bladder extending little, if any, beyond origin of anal. 



Origin of dorsal as in rhomhoicles, equidistant from tip of snout and 

 upper caudal fulcra or a little nearer caudal; the highest ray about 

 equal to the length of the head or shorter. Caudal broad and deeply 

 notched. The middle rays only ^ the length of the longest outer rays, 

 outer rays leathery. Anal short, emarginate, the tip of the longest 

 ray reaching tip of the last. Pectorals not reaching ventrals except 

 in 9,937 ; ventrals about f to vent. 



Plumbeous above, bright silvery below, indications of bright stripes 

 along the rows of scales above the lateral line and between the rows 

 below the lateral line. In 9,936 and 9,937 (preserved in formalin) 

 there is no metallic silvery and there is a dark band along the posterior 

 half of the lateral line, increasing in width and intensity toward the 

 tail. Xo. 9,937 evidentl}" in shape and color approaches rhomhoides 

 most closely. 



