THE RUDDER-FISHES 



Family LV. Kypliosidcv 



Herbivorous fishes, with incisors only in the front of the jaws; 

 body oblon<j: or elevated, with moderate or small scales; mouth mod- 

 erate, with incisor-like teeth in front; no molars; premaxillaries mod- 

 erately protractile; pseudobranchiae well developed; opercles entire; 

 gill-membranes separate, free from the isthmus; dorsal fin continuous 

 or divided, with lo to 15 rather strong spines; anal with 3 spines. 



A family with a good many species; shore-fishes, feeding largely on 

 green or olive alga;; chiefly found in the Mediterranean and in the 

 Pacific; most of them valued as food. About 6 genera and 10 species 

 within our limits. 



a. Soft parts of dorsal and anal (ins naked or only partly scaled; teeth 



in broad bands, all freely movable, none on vomer. 



b. Dorsal spines 14 or 15 Girclla, 4S0 



bb. Dorsal spines 12 or 13 Doydixodoii, 4s 1 



aa. Soft parts of dorsal and anal fins closely scaled; teeth more or less 



fixed, usually present on vomer. 



c. Top of head naked as far back as posterior margin of eyes. 



HcriJiosilla, 451 

 cc. Top of head as well as its sides and jaws closely scaled. 



d. Incisors strong, with horizontal backward projecting roots. 



e. incisor teeth well developed, each with a conspicuous horizontal 



process or root; caudal fin moderate, about as long as head. 



KypJiosus, 4S2 

 ee. Incisor teeth small, with inconspicuous roots; caudal much longer 



than head Scctator, 4s 9 



dd. Incisors very narrow, without evident roots Mcdiiiliiiuu 4S3 



GENUS GIRHLLA GRAY 



Body oblong-ovate, compressed, covered with rather large scales; 

 mouth small, with a series of tricuspid, movable incisors, behind 

 which is a broad band of similar smaller ones; no molars; no teeth 

 on vomer or tongue; cheeks with very small scales; opercles and top 

 of head chiefly naked; gill-rakers slender; dorsal fin rather low, XIV, 

 14, scaled at the base, forming an imperfect sheath; anal tin 111, 12, 

 the spines small, graduated; caudal lunate. 



450 



