494 Mr. C. T. Regan on the Origin and 



The principal genera may be arranged thus : — 



A. Mouth large, with the jaws and dentition nearly 



equally developed on both sides. Vertebras 40-50 

 (10-16 + 29-37). 



Hippoglossus, Atheresthes, Platysomatickthys, Hippoglos- 

 soides, Psettichthys, Eopsetta, and Liopsetta, from arctic and 

 northern seas. 



B. Mouth small, asymmetrical, the jaws and dentition 



more developed on the blind side. Vertebrae 35-65 

 (10-14 + 23-52). 



Pleuronichthys, Parophrys, Isopsetta, Limanda, Pleuro- 

 nectes, Platichthys, Microstomas, Oiyptocephalus, &c, from 

 arctic and northern seas, with Poscilopsetta, Boopsetta, and 

 JSematops, from the Indo-Pacific. 



I have examined specimens of Uippoglos&iis (vertebras 

 16 + 34), Hippoglossoides (13 + 31), Psetiichlhys (10 + 32), 

 Pleuronectes (10-11 + 24-30), Parophrys (13 + 24), and 

 Microstomias (12 + 36-37) . 



Subfamily 2. Samabin^!. 



Dorsal fin extending forward on snout either above or 

 below nasal organ of blind side ; pelvic fins supported by the 

 pelvic bones behind or below the cleitlira, asymmetrical, that 

 of the eyed side median and somewhat advanced. Pectoral 

 radials present ; hypocoracoids expanded. Vertebras 31 

 (10 + 21) ; prgecaudal parapophyses united to form closed 

 liasmal arches bearing the slender ribs at their extremities. 

 Mouth symmetrical, with the jaws and dentition nearly 

 equally developed on both sides. 



Genera : — Paralichthodes, Brackypleura, and Samaris, from 

 the Indo-Pacific. 



Well distinguished externally from the Pleuronectinse with 

 symmetrical mouth by their form, the absence of a distinct 

 caudal peduncle, the extension forward of the dorsal nearly 

 to the end of the snout, and the asymmetrically placed pelvic 

 fins, these three genera form a natural and well-marked group. 

 Paralichthodes differs from the others in that the nostrils of 

 the blind side appear below instead of just above the anterior 

 part of the dorsal fin, and Samaris is distinguished by the 

 more extended bases of the pelvic fins. 



1 have examined the skeleton in Braehypileura. 



