234 NATURAL SCIENCE. April, 



Platessinae, which is characterised by the small terminal, somewha 

 asymmetrical mouth, large eyes, dextral asymmetry of the body, 

 well-developed pectoral fins, vertical fins well separated, symmetry 

 and narrow bases of the pelvic fins, and usually strong anal spine. 



All the Platessinae are arctic or antarctic in distribution. 

 Consequently, all the known forms are completely reviewed in the 

 paper of Jordan and Goss, which makes the study of their characters 

 for the purpose of the present inquiry much easier. 



In this sub-family Jordan and Goss make our common dab the 

 type of a genus, Limanda, with the following characters : — There is 

 no accessory branch to the lateral line ; the lateral line has a distinct 

 arch in front ; the scales are rough, ctenoid, and imbricated ; the 

 vertebrae are forty in number. 



The authors recognise four species. One of these, called Limanda 

 beani, is doubtful. It is characterised by the shortness of the head, 

 which is contained 5^ times in the total length, instead of 3^ to 4^ 

 as in the other species. It was defined by Dr. Brown Goode, from 

 certain specimens taken in deep water off the southern coast of New 

 England, which were not seen by Jordan and Goss. Perhaps the 

 characters were individual variations or deformities. 



Limanda limanda, the European form, has no rugose prominences 

 above the operculum behind the interocular ridge. The fin-rays 

 are Dorsal, 65 to 78 ; Anal, 50 to 62 ; the scales along the lateral line, 

 86 to 96 ; the teeth in an irregular series. This species extends from 

 the Atlantic coasts of France along all the coasts of Northern Europe, 

 and on the coast of Iceland : it is absent from the Mediterranean. 



Limanda ferruginea is the dab of the American side of the Atlantic, 

 extending from New York to Labrador. It differs in having the 

 teeth more numerous, and in a more regular close-set series, in having 

 a more projecting snout, and rugose prominences above the operculum. 

 The fin-rays are a little more numerous, namely, Dorsal, 85 ; Anal, 62. 

 The scales are smaller and more numerous, namely, 100 along the 

 lateral line. The colour is brownish-olive, with numerous irregular 

 reddish spots. 



Limanda aspera is the dab of the North Pacific. It is distinguished 

 by somewhat marked characters, of which the principal are that there 

 is no angle between the snout and the profile of the head, and the 

 scales of the blind side are more or less rough, the scales of the upper 

 side rougher than in the other species. Specimens have been taken 

 on the coast of both Alaska and Kamtschatka. 



It seems, therefore, that while the species on opposite sides of the 

 Atlantic are different, those on opposite sides of the Pacific are the 

 same. But the localities Alaska and Kamtschatka are nearer than 

 Europe and Labrador. On the other hand, since the European dab 

 is found on the Iceland coast, there is no obvious reason why it should 

 not extend to the Greenland coast and thence to Labrador. 



This case offers a good contrast to that of Zeugoptenis. In the 



