[9] FLOUNDERS AND SOLES. 233 
li. Mouth very small, the teeth subequal, the maxillary less 
than one-third length of head. 
n. Teeth uniserial; vertebra 9 + 25 = 34.... ETROPUS, 22. 
nn. Teeth in villiform bands ....---- THYSANOPSETTA, 23. 
aa. Pectoral iin of blind side wanting ; eyes very close together; caudal fin subses- 
sile; teeth small, uniserial; mouth moderate; lateral 
line of eyed side arched, that of right side nearly straight; 
dorsal fin beginning on snout, its anterior rays not ex- 
serted, its rays all simple and very numerous; scales 
small; body thin, very elongate ; vertebre (sessilicauda) 
43; (deep-sea flouncers, of uncertain relationship). 
MONOLENE, 24. 
Subfamily IT1—ONCOPTERIN &. 
(Small-mouthed flounders, with the right ventral fin extending along 
the ridge of the abdomen, dorsal beginning at the snout, a bony promi- 
nence of some sort connected with its first ray; eyes and color on the 
right side.) 
a. Left side of snout with a horizontal slit-like cavity, into which a curved, bony, 
ray-like appendage is depressible; lateral line with an anterior arch and with 
numerous accessory branches nearly atright angles withit ; scales cycloid ; right 
ventral fin free from the anal fin; left ventral fin present; gill-rakers short and 
SIE TAUGIN.. oa doer ai GUC EHEE Ser Bcc BEAT AE ESIC DEIEDODE POH IDE ta eee ONCOPTERUS, 25. 
Subfamily IV.—PLATESSIN &. 
Mouth small, unsymmetrical, the jaws on the eyed side with nearly 
straight outline, the bones on the blind side strongly curved; dentition 
chiefly developed on the blind side; eyes large; edge of preopercle 
not hidden by the scales ; pectoral fins well developed; vertical fins well 
separated ; ventral fins nearly or quite symmetrical ; anal spine usually 
strong (obsolete in Microstomus). Body dextral (except frequently in 
Platichthys stellatus). Species arctic or subarctic in distribution. 
a. Vertebrz in moderate number (from 10 + 26 = 36 to 11+ 33 = 44); dorsal rays 
65 to 80; anal rays 45 to 60. 
b. Teeth small, acute, in several series; lateral line nearly straight, with an acces- 
sory dorsal branch; lower pharyngeals narrow, with small 
biserial teeth; scales cycloid. (Genera allied to Pleuronichthys). 
e. Lips thick—each with several longitudinal folds; dorsal fin beginning on the 
blind side ; vertebrz 38 to 40. .......... PLEURONICHTHYS, 26. 
cc. Lips simple; dorsal fin beginning on the median line; vertebre (quttulatus) 
TH gtk Ps cee 5) ae SO ee Ree ee HYPSOPSETTA, 27. 
bb. Teeth chiefly uniserial, all more or less blunt, conical or incisor-like. (Genera 
allied to Platessa). 
d. Lateral line with an accessory dorsal branch. 
e. Lateral line without distinct arch in front. 
Jf. Teeth compressed, incisor-like, close-set. 
g. Scales closely imbricated, mostly cycloid ; upper eye on median line; 
vertebra (vetulus) 11 + 33 = 44.._.........--.PAROPHRYS, 28. 
gg. Scales scarcely imbricated, all very strongly ctenoid; eyes both 
laters leases tote less a dann deaceweleaosee tote INOPSETTA, 29. 
