THE SHORE FISHES OF PERU 13 



Type. — The particular specimen designated to represent the species by the original 

 describer (holotype) ; other specimens studied at the same time and used with 

 the holotype in preparing the original description (paratypes) ; also the 

 species on which a genus is based (genotype). 



Type locality. — The particular place at which the type of a species was collected. 



Ventral plates. — Bony plates lying on the belly; only occasionally present. 



Vertical fins. — The fins placed on median line of body, that is, the dorsal, caudal, 

 and anal fins; used to distinguish them from the paired fins, namely, the pec- 

 toral and ventral fins. 



Villiform. — Said of minute, crowded teeth in bands or patches. 



Vomer. — A bone in the front part of the roof of the mouth, lying immediately 

 behind the premaxillaries, sometimes bearing teeth. 



SYSTEMATIC CATALOG 



KEY TO THE FAMILIES 



/. Leptocardii (lancelets): Body elongate, compressed; mouth a mere slit; 

 skeleton cartilaginous; skull undeveloped; gill openings consisting of nu- 

 merous slits Branchiostoinidae (p. 21) 



//. Selachii (sharks, skates and rays, and chimaeras): Body variously shaped; 

 skeleton cartilaginous; skull imperfectly developed; mouth well formed, 

 with jaws separable from the skull, or the upper one more or less coalesced 

 with it (in chimaeras) ; gill openings slitlike, 4 to 7 on each side, or with a 

 single opening on each side leading to 4 slits (in chimaeras) ; gills attached 

 to skin; males with large claspers attached to ventral fins. 

 a. Gill openings consisting of 5 to 7 external slits; teeth distinct. 



b. Body usually rounded, typically fishlike, occasionally depressed; gill slits 

 lateral or only partly inferior; pectoral fins sometimes expanded but 

 not continuous with head. 



c. Both dorsal fins provided with a strong spine Heterodontidae (p. 22) 



cc. Dorsal fins without spines. 



d. First dorsal over or behind ventral. 



e. Body slender; size small; teeth of medium size, more or less 

 triangular, often tricuspid; lower lobe of caudal scarcely 



exserted Scylliorhinidae (p. 24) 



ee. Body massive; size enormous; teeth small, numerous, subconic; 



lower lobe of caudal large Rhincodontidae (p. 26) 



dd. First dorsal well in advance of ventral. 



/. Head greatly depressed, with lateral extensions, more or less 



hammer-shaped Sphymidae (p. 26) 



//. Head normally shaped, without lateral extensions. 



g. Gill slits of moderate length, not nearly meeting at midline 

 of throat, one or more slits above base of pectoral; tail 



without lateral keel Qaleorhinidae (p. 28) 



gg. Gill slits very long, nearly meeting at midline of throat, 

 all in front of pectoral; tail with keel; size very large. 



Cetorhinidae (p. 44) 



bb. Body much depressed; gill slits inferior (or partly lateral as in Squa- 



tinidae) ; pectoral fins greatly expanded, confluent with the head 



(except in Squatinidae) . 



h. Pectoral fins not entirely confluent with head; nostrils situated on front 



margin of snout Squatinidae (p. 46) 



