THE SHORE FISHES OF PERU 21 



Vp" . Mouth small; teeth in jaws forming a continuous plate; 

 body not with normal scales, generally naked or with 

 prickles; capable of great inflation. 



Tetraodontidae (p. 484) 



oo" . Dorsal fins 2, the first consisting of 3 spines; body covered 



with rather large bony scales, forming a coat of mail; a 



large median ventral spine present. .Balistidae (p. 480) 



aa. Eyes and pigment restricted to one side. 



q" . Preopercle with a free margin; eyes moderate, well separated; eyes and 



pigment normally on left side Bothidae (p. 460) 



qq" . Preopercular margin not free, being hidden by skin and scales; eyes very 

 smaU and very close together. 

 r" . Body short, more or less oval; eyes and pigment on right side; caudal 



free from dorsal and anal Soleidae (p. 472) 



rr". Body elongate, more or less tongue-shaped; eyes and pigment on left 

 side; caudal continuous with dorsal and anal. 



Cynoglossidae (p. 473) 



Family BRANCHIOSTOMIDAE: Lancelets 



Body elongate, compressed, pointed at each end, deepest in middle, 

 naked; eye rudimentary; mouth inferior, an elongate median fissure, 

 surrounded by rather long stiff cirri; dorsal fin represented by a low 

 fold on the back; and usually also represented by at least a rudi- 

 mentary fold; gonads arranged in pahs of pouches along the ventral 

 surface of the body in a large pouch formed by a continuation of the 

 body wall forming free folds, leaving an opening along the ventral 

 surface; color nearly or entirely wanting, translucent in life. A single 

 genus and species occurs in the Peruvian collections studied. 



Genus BRANCHIOSTOMA Costa, 1834 



Rostral process not especially long, represented only by a dermal 

 flap. Other characters are suflQciently indicated in the description 

 of the family. 



These lancelets usually occur on sandy shores in warm water. 

 Some evidence has been found indicating that they embed themselves 

 mostly during the day and become active at night. The anus is 

 consistently situated on the left side of the anal fold in rather niunerous 

 specimens examined of three different species from the Pacific coast 

 of the Americas. 



BRANCHIOSTOMA ELONGATUM Sundevall 



Branchiostoma elongatum Sundevall, 1852, p. 147, Chincha Island, Peru (original 

 description). — Andrews, 1893, pp. 233, 238, 242. — Jordan and Evermann, 

 1896, p. 4, footnote (diagnosis, relationship). — Regan, 1913, p. 278, Lobos de 

 Tierra, Peru (specimens from 5 to 8 fathoms). — Fowler, 1941a, p. 219 

 (references) . 



Muscular rings, or myomeres, 79 to 82 in number, 28 to 30 of these 

 behind gonad-bearing part of body; rostral prolongation a broad 



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