THE SHORE FISHES OF PERU 15 



ii. Snout and jaws not produced (in adults) ; body not very slender, 

 often rather short, compressed. 

 I. Pectorals, and sometimes ventrals also, very large, winglike, 



used as organs for flight Ezocoetidae (p. 147) 



II. Pectorals and ventrals not especially large. 



m. A bony plate present between arms of lower jaw; branch- 



iostegals about 25 to 35 Elopidae (p. 78) 



mm. Bony plate between arms of lower jaw wanting; branch- 

 iostegals about 6 to 15. 

 n. Mouth moderate, terminal or more or less superior, gen- 

 erally oblique Clupeidae (see also p") (p. 80) 



nn. Mouth large, horizontal, with overhanging, piglike snout. 



Engraulidae (p. 96) 

 hh. Dorsal fins 2, first composed of spines. 



0. Pectoral in 2 parts, lower part consisting of free filamentous rays. 



Polynemidae (p. 434) 

 00. Pectoral not in 2 parts, without free rays. 



p. Head long; jaws long and strong, provided with strong teeth of 



unequal size Sphyraenidae (p. 418) 



pp. Head not especially long; jaws not produced, rather weak; 

 teeth minute or wanting. 

 q. First dorsal with 3 to 9 flexible spines; anal with a single weak 



spine Atherinidae (p. 428) 



qq. First dorsal with 4 strong stiff spines; anal with 3 stiff spines 



(very young with only 2) Mugilidae (p. 420) 



Ventral fins thoracic or jugular (that is, attached somewhere to the 



thorax or chest, or under the head). 

 r. Ventral fins thoracic, each fin composed of 1 spine and 5 soft rays ex- 

 cept in Gempylidae, Merlucciidae, and sometimes Cottidae. 

 s. Ventral fins separate and distinct, not forming a sucking disk on 

 chest. 

 t. Top of head with a large sucking disk composed of crosswise par- 

 titions and a lengthwise septum Echeneidae (p. 479) 



tt. Head without a sucking disk. 



u. Jaws, especially the upper one, greatly produced, forming a 

 spike or bill; 2 dorsal fins, first one very long and sometime 

 very high, second very small (large game fishes). 



Istiophoridae (p. 378) 



uu. Jaws not greatly produced; dorsal fin single or double, first one, 



if separate, usually equal to or shorter than second. 



V. Suborbital with a bonj ridge or stay; head partly or wholly 



encased in spinous bony plates. 



w. Pectoral fins very long, winglike, with the 3 lowermost rays 



free; dorsal fins 2 Triglidae (p. 454) 



WW. Pectoral fins only moderately long, not winglike, without 

 free rays; dorsal fin single. 

 X. Gill opening wide, extending forward to isthmus; mouth 



large, wide Scorpaenidae (p. 437) 



XX. Gill opening restricted to side, above base of pectoral; 



mouth small Congiopodidae (p. 456) 



vv. Suborbital stay wanting; head not encased in spinous bony 

 plates. 

 y. Gill arches 4, a slit behind fourth. 



