[9] FLOUNDERS AND SOLES, 233 



II. Mouth very small, the teeth subequal, the maxillary less 

 than one-third length of head. 



v. Teeth uniserial ; vertebra? 9 -{- 25 = 34 Etropus, 22. 



nn. Teeth in villiform bands Thysaxopsetta, 23. 



aa. Pectoral tin 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 beginniug on snout, its anterior rays not ex- 

 serted, its rays all simple and very numerous : scales 

 small ; body thin, very elongate ; vertebrae (sessilicauda) 

 43; (deep-sea flounders, of uncertain relationship). 



Monolene, 24. 



Subfamily III -ONCOPTEKIM. 



(Sinall-inouthed 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 5 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 at right angles with it ; scales cycloid ; right 

 ventral fin free from the aual fin ; left ventral fin present ; gill-rakers short and 

 slender Oncopterus, 25. 



Subfamily IV.-PLATESSINJE. 



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 ; aual spine usually 

 strong (obsolete in Microstomas). Body dextral (except frequently in 

 Platichthys stellatus). Species arctic or subarctic in distribution. 



a. Vertebra? in moderate number (from 10 -f 2(5 = 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 Pleuronichlhys). 

 c. Lips thick — each with several longitudinal folds ; dorsal fin beginning on the 



blind side ; vertebrae 38 to 40 Pleuronichthys, 26. 



cc. Lips simple; dorsal fin beginning on the median line; vertebrae (guttulatus) 



11 + 24 = 35 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. 

 /. Teeth compressed, incisor-like, close-set. 



g. Scales closely imbricated, mostly cycloid ; upper eye on median line; 



vertebra? (vctulus) 11 -f 33 = 44 Parophrys,.28. 



gg. Scales scarcely imbricated, all very strongly ctenoid ; eyes both 

 lateral *. Inopsetta, 29. 



