of the Fisher 1/ Board, for Scot In ml 



353 



i.e. the eye of the Wind side, which is on the ridge of the head, looking 

 almost vertically upwards. This position, which appears to be the 

 normal one, recalls the abnormal specimens of other species with arrested 

 migration of the eye of the blind side which are sometimes found, e.g. 

 Turbot. Whether these two species are in reality the nearest modern 

 representatives to the primitive ancestors, or whether they are specialisa- 

 tions just as Cynoglossus of the Soleinre is a specialisation at the other 

 extreme, it is impossible to say. In the present paper, however, it is 

 assumed that they are the most primitive forms, and hence the Hippo- 

 glossinse form the earliest or first family of the Heterosomata. 



The distribution of the various genera here included under the 

 Hippogiossinse is noteworthy. They all belong to the Arctic and 

 northern portions of the temperate regions. 



Sub-Fam. Pleuronectince. 

 (1), (2), (3), as in Hippoglossinas. 



(4) The anterior extremity of the dorsal fin is inclined towards 



the blind side of the head, and lies posterior to the nasal 

 organ of that side, which is (usually) on the ridge of the 

 head. 



(5) Mouth unsymmetrical, dentition more developed on blind 



side ; gape small ; under jaw more prominent. 



(6) Eyes on right side as a rule, large. 



The following genera are included under this sub-family : — 



Species Examined. 



Genus. 



Distribution. 



P. comuta 



(?) 

 ( ? ) 



Lepidopsdta hihneata . 

 L. limanda . . \ 

 L. aspera . . / 



CO 



Platichthys stellatus 

 P, Jiesus . . -\ 

 P. p/atessa . . 1 

 P. microcephalics j 

 ! P. cynoglossus . J 



Parophrys, Gtr. 

 Pleuronichthys, Girard. 

 Inopsetta, Jordan and"\ 

 Goss. 1 

 Isopsetta, Lockington. j 

 Lepidopsetta, Gill. J 



Limanda, Gottsche. 



Liopsetta, Gill. 



Platichthys, Girard. 

 Pleuronectes, L. 



North America and Japan. 

 North Pacific. 



Pacific coasts of North America. 



North Atlantic and North Pacific. 



North Atlantic and North Pacific 

 (American). 

 | North Pacific. 



North Atlantic and North Pacific. 



Various other genera are included by Jordan within this family, but 

 since they are generally classified by other writers as species under the 

 above genera, it is considered advisable to omit them for the present. 

 For example, Pleuronectes microcephalus has been relegated to a new 

 genus, Microstomus, and P. cynoglossus to another, Glyptocephalus. 

 Examination of the internal structure of the former species shows that 

 it is very closely allied to the plaice, P. platessa, even to the presence of 

 the characteristic tubercles on the otic regions of the skull. P. cynoglossus 

 seems the next step to P. microcephalus in the specialisation away from 

 the Plaice, and it is a pity to subdivide these species into separate genera 

 when their inclusion within one genus more fitly expresses their 

 affinities. 



This sub-family is well marked off from the preceding, to which it is most 

 nearly allied, and from which it has probably been derived, by the peculiar 

 shape and size of the mouth. Amongst the European forms there seem 

 to be no transition stages, but amongst the American Jordan mentions 

 that Isopsetta closely resembles Psettichthysoi the family of Hippogiossinse. 



