THE SHORE FISHES OF PERU 93 



missing; pectorals rather large, often equal to or longer than the head. 

 A single species, which seems to be new, occurs in the collections 

 from Peru that are at hand for study. 



OPISTHOPTERUS EQUATORIAUS, new species 



Figure 18 



Head 5.3 to 5.8; depth 3.4 to 3.55; D. 11 or 12; A. 59 to 62; P. 12; 

 scales mostly lost, about 50; vertebrae 47 (one specimen dissected). 



Body very strongly compressed, ventral outline much more strongly 

 convex than the dorsal ; greatest thickness scarcely exceeding diameter 

 of eye; caudal peduncle much shorter than deep, 2.45 to 2.6 in head; 

 head very small, its dorsal outline straight and horizontal, and much 

 lower than nape; snout shorter than eye, 5.2 to 6.0 in head; eye 3.15 

 to 3.4; interorbital 9.0 to 11.0; mouth superior, nearly vertical; 

 maxillary about as wide as pupil, extending only slightly beyond 

 anterior margin of eye, 2.5 to 2.85 in head; mandible 2.45 to 2.6; 

 teeth all minute; gill rakers about as long as pupil, 10 on upper and 



Figure 18. — Opisthopterus equatorialis, new species. From the type, 160 mm. long, Puerto 

 Pizarro, Peru (U.S.N.M. No. 127807). 



25 on lower limb of first arch ; scales thin, nearly all lost, with some- 

 what irregular margins; ventral scutes sharp, 26 to 28; dorsal rather 

 weakly developed, far behind middle of body, about over middle of 

 anal base, its origin about half as far from base of caudal as from tip 

 of mandible; caudal fin (injured) broadly forked, apparently shorter 

 than head; anal very long and low, its origin about an eye's diameter 

 nearer tip of mandible than base of caudal, its base 1.85 to 1.95 in 

 length; pectoral large, exceeding length of head, 4.5 to 4.8 in length. 



Color of preserved specimens plain ; sides of head silvery ; a distinct 

 silvery band, about the width of pupil extending from upper angle 

 of opercle to base of caudal; upper parts of head and back with dusky 

 dots, forming a more or less definite dark band on midline of at least 

 most of length; fins all with dusky points. 



This species is represented in the Peruvian collection made by the 

 mission by 6 specimens, about 155 to 165 mm, (caudal fins injured) 

 in total length (130 to 138 mm. to base of caudal), all caught in an 

 otter trawl in the Gulf of Guayaquil, off Puerto Pizarro. A specimen 



