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Part III. — 'Eighteenth Annual Report 



It is probable, therefore, that the transitional forms existed in the 

 European waters at one time, but have now disappeared. On the other 

 hand, in the peculiar shape of the mouth and in the presence of the 

 " Sole-form " in such as P. microcephalus and P. cynoglossus we see the 

 close affinities of this family to the Soleinae — not that these are necessarily 

 the forms which mark the transitional stages, but they indicate how the 

 Soleinae might have been derived from the Pleuronectinae. 



The distribution of the genera included within this family is more 

 southerly than that of the Hippoglossinae, but they are for the most 

 part confined to the more northerly portions of the temperate zone. 



Sub-Fam. Hippoglosso-rhombince. 



(1) As in Hippoglossinae. 



(2) Olfactory laminae arranged transversely about a median 

 rachis. 



(3) Ventral fins varying from the symmetrical condition of the 



Hippoglossinae to a partial form of the asymmetrical 

 condition in the Khombinae ; in all, the pubic bones are 

 wholly behind the clavicles, to which, when the fins are 

 asymmetrical, the anterior of the pubic bones is sometimes 

 attached. 



(4) As in Pleuronectinae, but the anterior extremity of dorsal fin 

 is continued forward in some genera to nasal organ of blind 

 side. 



(5) As in Hippoglossinae. 



(6) Eyes on left side as a rule, but very variable, large. 



These are the characters which unite together a number of genera 

 some of which have been hitherto classed with the Halibuts, and others 

 with the Turbots. They are separated from the former group by having 

 the form of olfactory organ which is found in the latter, whilst 

 they are more akin to the Halibut-group in almost all other 

 characters. The genera which have hitherto been included with the 

 Halibut-group are Paralichthys, Pseudorhombus* Psettodes, and Tephritis. 

 These are evidently distinguished from the Halibuts by character (2), in 

 that they have the olfactory laminae arranged transversely about a 

 median rachis. The most remarkable form is Psettodes, which has 

 hitherto been classed with the Halibuts and considered to have affinities 

 to the most primitive, viz. Atheresthes. These affinities, displayed in 

 the general form and structure and in teeth, are certainly striking, and 

 lead to the conclusion that Psettodes is either a direct offshoot from the 

 Halibut, or, if it has come through any intermediate forms, that it has 

 assumed these characters by specialisation to its peculiar habits of life. 

 The structure of the olfactory organ, however, seems a sufficient reason 

 for removing this genus along with Paralichthys from the Halibut 

 group and placing it in this family. In addition to the structure of 

 the olfactory organ, there are other characteristics which separate it 

 from the Halibuts. In the Halibut-group the eyes are almost invariably 

 on the right side. In this genus, as in the other genera of this family, 

 the eyes may be on the left or right side, but generally on the left. 

 Thus, of nine examples mentioned by Giinther in his Catalogue (vol. 

 IV., p. 402), five had the eyes on the left side, four on the right. The 

 specimen examined by myself, further, had no pyloric caeca — a 

 characteristic of the Sole-group. Lastly, the distribution of this genus 

 is southerly, where that of the Halibuts is northerly, as already noted. 



With regard to Paralichthys, there is less objection to removing it 

 from the Halibuts than there is with Psettodes. With the exception of 

 * The American writers include Pseudorhombus under Paralichthys. 



