340 BULLETIN 189, UNITED STATES NATIONAL MUSEUM 



61 mm. to base of caudal) long, furnished by the Mission, These 

 fish are from Lobos de Afuera, where R. E. Coker also secured a small 

 specimen, which is at hand. As it has been dry, it is of little value, 

 though it agrees in the number of fin rays, scales, and gill rakers. 



The Peruvian examples are much darker than the Panama speci- 

 mens, with which they were compared. They differ also in having the 

 lobes of the dorsal, caudal, and anal less strongly angulate, and the 

 teeth seem to be broader and more definitely bicuspid. However, in 

 the study of rather numerous specimens from Panama Bay I found 

 much variation in these and some other characters. The significance 

 of the variation can be determined only through a thorough study of 

 large series of specimens from the range of the genus in at least the 

 Western Hemisphere. About 10 nominal American species have been 

 described, most of which have at some time been referred to syn- 

 onymy, often seemingly without much more evidence than the orig- 

 inal describer had for believing his specimens to represent new species. 



Range. — Both coasts of America. On the Atlantic from Cape Cod 

 to Uruguay, and on the Pacific from Baja California to northern 

 Peru and the Galapagos Islands. 



Genus NEXILOSUS Heller and Snodgrass, 1903 



Body ovate, the depth generally rather less than half the length; 

 teeth fixed, in a single series in each jaw, each tooth slightly broad- 

 ened at tip, with an even (unindented) margin, suborbital adnate to 

 cheek anteriorly, with free margin posteriorly (not fully adnate, as 

 implied in the original description), being intermediate of Nexilarius 

 in which it is fully adnate to the cheek, and Abudefduf in which its 

 lower margin is free for its full length. It differs from both genera 

 mentioned in having narrower teeth without indented margins, and 

 from Pomacentrus in having preopercular and suborbital margins 

 entire (not serrated). 



A single species is known. 



NEXILOSUS LATIFRONS (Tschndi) 



CASTAfJETA; Sargo DE pena; Coco; Coquito 



Pomacentrus laiifrons Tschudi, 1845, p. 17, Huacho, Peru (original description). 



Nexilosus albemarleus Heller and Snodgrass, 1903, p. 204, pi. 8, Galdpagos 

 Islands (original description). — Snodgrass and Heller, 1905, p. 391, Tagus 

 Cove, Elizabeth Bay and Iguana Cove, Albemarle Island, Galdpagos. 



Nexilosus latifrons Evermann and Radcliffe, 1917, p. 121, MoUendo, Guanape 

 North Island, and Lobos de Afuera, Peru (synonymy; description; range). — 

 Nichols and Murphy, 1922, p. 511, South Chincha Island, Peru. 



Head 3.0 to 3.5; depth 1.8 to 2.0; D. XIII, 17 to 19; A. II, 13 or 14; 

 P. 20 to 22; scales (vertical series along middle of side) 28 or 29; 

 vertebrae 26. 



Body rather short, deep, compressed, its greatest thickness some- 



