240 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



anterior margin of the eye in all the specimens studied. As to its 

 proportionate length the measurements are unsatisfactory, as in 

 many specimens the highly protractile premaxillaries are drawn 

 forward, causing a distortion. The second spine of the anal is very 

 variable in length, and therefore its proportionate length does not 

 seem to be of any specific value, for example, in 7 small specimens 

 from the Atlantic its length in the head varies from 2.0 to 3.4, and in 6 

 small specimens from the Pacific the range is 1.6 to 2.5, 



The number of dorsal spines and rays is constantly IX, 10, and for 

 the anal III, 7 in all specimens from each coast examined. Other 

 proportions, in which those for Atlantic specimens in each instance 

 are stated first, are: Depth in length 2.25 to 2.5, 2.25 to 2.5; pectoral 

 2.6 to 2.7, 2.6 to 2.7. Eye in head 2.7 to 3.25, 2.5 to 3.25; snout 2.25 

 to 3. 6, 2.75 to 3.36; interorbital 3.2 to 3.7; 3.3 to 3.8; caudal peduncle 

 2.6 to 3.0, 2.65 to 3.0. 



Range. — Both coasts of America; on the Atlantic from Florida to 

 northern South America, and on the Pacific from Baja California 

 to Peru. 



Genus DIAPTERUS Ranzani, 1840 



Body rather short and deep, quite compressed; preopercle, and 

 sometimes preorbital, serrate; second or third dorsal spine, and second 

 anal spine rather long, and more or less enlarged; second interhaemal 

 spine long, spear-shaped, not hollow. 



KEY TO THE SPECIES 



a. Preorbital entire; dorsal with 9 spines and 9 or 10 soft rays. 



peruvianus (p. 240) 

 aa. Preorbital distinctly serrate; dorsal with 10 spines and 9 soft rays. 



periche (p. 241) 



DIAPTERUS PERUVIANUS (CuTier and Valenciennes) 



Periche 



Gerres peruvianus Cuvier and Valenciennes, 1830, p. 467, Paita, Peru (original 

 description). — Evermann and Radcliffe, 1917, p. 92, Capon, Peru (ref- 

 erences; description). 



Diapterus peruvianus Meek and Hildebrand, 1925, p. 597, Panama Bay, and 

 adjacent brackish tide streams (synonymy; description; range). — Tortonese, 

 1939b, p. 304, Callao, Peru. 



Head 2.9 to 3.05; depth 1.9 to 2.0; D. IX, 9 or 10; A. Ill, 8; P. 15 

 or 16; scales 35 to 38. 



Body short, deep, rather strongly compressed, its greatest thickness 

 about a third its depth; back high; profile from snout to nape straight, 

 or even slightly concave over the eyes; outline under snout and an- 

 terior part of eye dropping rather abruptly, slightly concave; caudal 

 peduncle short, strongly compressed, 2.4 to 2.5 in head ; snout moder- 

 ately pointed, 3.7 to 3.8; eye 2.5 to 3.1; interorbital 2.5 to 3.4; mouth 



