NATURAL SCIENCES OF PHILADELPHIA. 361 



fovere or pits in the cranium and preoperculum ; orbital ridge 

 prominent, narrow, and curved upwards towards tlie lateral line 

 (with no bony tubercles). 



Eyes moderate, approximated, the upper (in typical species) 

 somewhat further back than the lower, mostly in the anterior third 

 of head. 



Nostrils of the ej^ed side parallel with the axis of the body ; 

 the posterior patulous, and above the supraorbital crest ; the an- 

 terior tubular, and near tiie border of the snout; those of the 

 blind side in an oblique row ; the posterior patulous ; the " ante- 

 rior" tubular. 



3Ioufh very small, with the cleft very oblique, deeper and less 

 oblique (the supramaxillary being longer) on the blind side. 

 Lower jaw scarcely prominent, with a declining obtusely angular 

 (not tuberculated) chin. 



Lips moderate and simple, free all around. 



Tongue small and scarcely free. 



Teeth fixed, uniserial, on the blind side approximated and with 

 compressed squarish crowns ; on the eyed side (1) similar or (2) 

 more distant and obtusely conic. (Palate unarmed.) 



Branchial apertures closed above the opercula, with the mem- 

 brane free below. 



Branchiostegal rays seven. 



Dorsal fin with its rays simple, in large number (100-120); with 

 its origin above the middle of the upper orbit, with the foremost 

 and hindmost rays (when at rest) converging, and the rest erect. 



Anal fin with its rays simple, in large number (90-105), with 

 its foremost and hindmost rays converging, but the rest erect; 

 preceded in front by a well-defined spur-like spine curved for- 

 wards. 



Caudal fin convex or angulated behind. 



Pectoral fins small, obliquely rounded behind, and with branched 

 rays. 



Ventral fin subbrachial, normally -developed. 



Type^ Pleuronectes cynoglossus, Linn. 



This genus is well distinguished by the elongated and com- 

 pressed body covered by cycloid scales, the straight lateral line, 

 the small head with its well-defined foveje (showing through the 

 scaly skin) of the cranial and preopercular regions, the numerous 

 dorsal and anal rays, and the preanal spur-like spine. Three 

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