of the Fishery Board for Scotland. 



357 



►Sub-fam. Ehombince * 



(1) As in Hippoglossinse . 



(2) As in Hippoglosso-rhombinse. 



(3) Ventral fins asymmetrical, the anterior extends anteriorly 



beyond the base of the clavicles ; the laminar portion of one 

 or both of the pubic bones is continued forward by a plate 

 of cartilage as far as the lower prong of the urohyal. 



(4) Nasal organ of the blind side lies entirely on the blind side 



of the head under the anterior extremity of the dorsal fin. 



(5) As in Hippoglossinse. t 



(6) Eyes on left side. 



The following genera are now included in this family : — 



Species Examined. 



Genus. 



Distribution. 



R. mancus 



(?) 

 (?) 



A. grohmanni 

 . 1 . laterna 



L. boscii . . \ 

 L. tvhiff . . / 

 S. unimacvdatus . \ 

 S. norvegicus . . / 

 Z. punctatus . 

 R. leer is \ 

 R. maxim us I 



B. mceoticus) 



(?) 



P. ocellatus . . (?) 



(?) 



Rhomboidichthys, Bl. 



(Platophrys, Swainson). 

 Perissias, J ordan and 



E verm arm. 

 Eugyophrys, Jordan and 



Bollman. 



Arnoglossus, Ron. 

 (Platophrys, Swainson). 



Lepido rhombus, Gtr. 



Scopthalmus, Bon. 

 Zeugopterus, Gottsche. 



Rhombus,* Kl. 



Etropus, Jordan and 

 Gilbert. 

 Psammodiscus, Gtr. 



Monolene, Goode. 



Sub-tropical regions of Atlantic 



and Pacific. 

 Gulf of California. 



Coast of Panama. 



Bub-tropical regions of Pacific 

 and Atlantic. 



Tempei'ate seas of Europe. 



Do. 

 Do. 



Temperate regions of North 

 Atlantic. 



Sub - temperate regions of 

 America. 



(?) 



Tropical and sub-temperate 

 regions of Atlantic. 



* This genus has been variously styled by the above mentioned authors, Pselta, 

 Pleuronectus, Bothus. As the reasons for adopting these are somewhat hazy, there is 

 insufficient ground for departing from the now familiar term Rhombus. 



Under previous classifications this sub- family was more clearly 

 separated from the other families of the Heterosomata than it is under 

 the present. And if the Turbot (E. maximus), which was formerly the 

 type of the family, were contrasted directly with the Pleuronectinse and 

 the Hippoglossinse. we should be inclined to think that the Heterosomata 

 had had two distinct sources of origin. It has been shown here, however, 

 that Citharus and its allied genera form a natural transition from the 

 Hippoglossinse to the Rhombinse, and that the latter family has first made 

 its appearance in some form akin to A?'?wglossus, if not in Arnoglossus 

 itself. It is most probable, indeed, that the Rhombinse had their origin 

 in the sub-temperate or tropical zones, and thence migrated north- 

 wards. The Turbot, Whiff, and Topknots are specialisations along- 

 certain lines away from the main body of the Heterosomata. 



* This sub-family has been variously called R/tombince, Gill ; Pleuronectince, Jordan and 

 Goss ; Bothiuce, Smitt ; Psettince, Jordan and Evermann, Gill. Each of these ia well 

 supported by weighty reasons, and one has therefore a considerable latitude of choice. 

 In deciding upon Rhombinop, for the sub-family as above restricted, I have taken into 

 consideration not only questions of priority, but also the fact that Rhombus is now the 

 customary and recognised term for the type of this sub-family, amongst European 

 ichthyologists at least. 



f According to Jordan and Evermann (33, p. 2687), Etropus is an exception, having a 

 small mouth, as in the Pleuronectidce. 



