230 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [6] 
bb. Mouth unsymmetrical, the jaws on the eyed side with nearly straight outline, 
the bones on the blind side strongly curved; teeth chiefly on the blind 
side. 
d. Ventral fins unsymmetrical, that of the eyed side extended along the ridge 
of the abdomen, snout with a free ray or other appendage in connection 
with the first ray of the dorsal. Eyes and color op the right side. 
ONCOPTFRIN& III. 
dd. Ventral fins nearly or quite symmetrical, that of the eyed side with short 
base; eyes and color on the right side (with occasional exceptions). 
PLATESSIN IV. 
aa, Soles. Edge of preopercle adnate, usually obscured by the scales; mouth very 
small, much twisted toward the blind side, and with rudimentary teeth; 
pectoral and ventral fins generally small, occasionally obsolete. 
e. Eyes on the right side, separated by a bony ridge ........-.--. SOLEINE V. 
ee. Eyes on the left side, not separated by a bony ridge....CYNOGLOSSIN VI. 
ANALYSIS OF GENERA OF PLEURONECTIDA FOUND IN AMERICA AND 
EUROPE. 
Subfamily I.—HIPPOGLOSSIN &. 
«a 
(Large-mouthed flounders with the ventral fins symmetrical. ) 
Mouth symmetrical, the jaws and the dentition nearly equally devel- 
oped on both sides; gape usually wide, the maxillary more than one- 
third length of head. Lower pharyngeals narrow, usually with but one 
or two rows of sharp teeth ; teeth in jaws usually acute. Eyes large; 
edge of preopercle free. Pectoral and ventral fins well developed, the 
ventral fins similar in position and in form of base, the ventral fin of the - 
eyed side not being attached along the ridge of the abdomen. Septum 
of gill cavity without foramen. 
a. Vertebre and fin-rays much increased in number (the vertebrae about 50, the dorsal rays 
about 100, the analrays about 85) ; body comparatively elongate ; 
caudal fin lunate ; lateral line simple; anal spine mostly obso- 
lete. Dextral species, Arctic in distribution. (Genera allied to 
Hippoglossus. ) 
ce. Large teeth in both jaws arrow-shaped, biserial, some of them depressible; upper 
eye with vertical range; gill-rakers short; scales deciduous, cili- 
ated ; lateral line without arch; flesh soft. Vertebrie (stomias) 
Dea 3) =o 40s co inimale ae eam csiee evan ce eee ATHERESTHES, 1. 
ec. Large teeth not arrow-shaped, biserial above, uniserial below; scales very 
small, cycloid; gill-rakers long and slender; eyes strictly lateral. 
d. Lateral line without anterior arch; lower pharyngeal teeth uniserial. 
PLATYSOMATICHTHYS, 2. 
dd. Lateral line with an interior arch; lower pharyngeal teeth biserial ; vertebrie 
(hippoglossus) 164-34=50 -...--....-...----.-- HIPPOGLOSSUS, 3. 
aa. Vertebre and fin-rays in moderate number (vertebrae less than 46, dorsal rays less. 
than 95, anal rays less than 75); caudal fin double truncate or 
rounded, the median rays longest. 
Jf. Lateral line without distinct anterior arch; vertebra, 40 to 46; body nor- 
mally dextral;* caudal peduncle distinct ; scales ciliated ; anal 
spine usually strong. Species of subarctic distribution. (Genera 
allied to Hippoglossoides.) 
*Frequentl y sinistral in Hippoglossoides elassodon. 
