PISHES OF WEST COAST OF PERU. 121 



This species is easily distinguislied from Chromis crusma by tlie 

 shorter head, shorter pectoral (in this species it is equal to or less 

 than head; in cmsma, it is always longer than the head) ; by the 

 differences in the fin formulas of dorsal and anal and by the slenderer, 

 more compressed body, especially anteriorly. 



Cuvier and Valenciennes note that the example from Juan Fer- 

 nandez differed from the others in having the vertical border of the 

 preopercle straight instead of concave and the angle more acute, the 

 upper lobe of the caudal longer and more pointed, causing the fork- 

 ing of the fin to appear deeper. These characters do not appear to 

 be of specific importance in separating this species. In our examples 

 of each species the straightness of the vertical border of the pre- 

 opercle varies, as does the forking of the caudal lobes. This species 

 is found in the vicinity of the small island groups on the coasts of 

 Peru and Chile. 



Genus NEXILOSUS Heller and Snodgrass. 



148. NEXILOSUS LATIFRONS (Tschudi). 

 OASTANETA; SARGO DE PENA. 



Pomacentrus laUfrons Tschudi, Fauna Peruana, Ichth., 1845, p. 17; 



Huacho, Peru.— GuNTHER, Cat. Fish. Brit. Mus., vol. 4, 1862, p. 34. 

 Olyphidodon latifrons Steindachner, Fauna Chilensis, 1898, p. 316. 

 Eupomacentrus latrifrons Abbott, Marine Fishes of Peru, Proc. Acad. 



Nat. Sci. Phila., 1899, p. 358. 

 Abudefduf laUfrons Delfin, Cat. Peces de Chile, 1901, p. 75. 

 Nexilosus albemarleus Heller and Snodgrass, Proc. Washington Acad. 



Sci., vol. 5, pi. 8, 1908, p. 204; Albermarle Island. — Snodgrass and 



Heller, Shore Fishes of the Galapagos Islands, Proc. Washington 



Acad. Sci., vol. 6, 1905, p. 391. 



One specimen, field No. 509, 20.3 cm. in length from Mollendo; 

 two, field Nos. 09171-2, respectively 19 and 14.6 cm. in length, from 

 Guanape North Island ; one, field No. 09143, 13.4 cm. in length, and 

 three young examples, field No. 278, 2 cm. in length, from Lobos de 

 Afuera (the small individuals taken from a small tidal pool). 



Head 3.2 (4 total) in length; depth 1.97 (2.5) ; eye 4.9 in head, 1.9 

 in snout, 2.2 in distance between lower edge of orbit and lower edge 

 of preopercle ; preorbital 1.11 in eye ; snout 2.5 in head ; D. XIII, 18 ; 

 A. II, 14; scales 4-27-12, 22 pores. 



Body ovate, deep, rather thick, curvature of dorsal outline greater 

 and more regular than that of the ventral outline; snout moderate, 

 blunt: mouth small, nearly horizontal, lips thick; teeth well devel- 

 oped, in a single series, compressed at tips, entire, incisor-like; 

 nostril very small, slightly above lower level of orbit; suborbital 

 adnate to cheek, lower free portion distinct; vertical border of pre- 

 opercle nearly straight, the lower border rounded ; opercle ending in 



