470 M ERISTIC VARIATION. [PART I. 



processes by which the dorsal fin comes to stand where it does. \Ve 

 are accustomed to think of the repetition of the fin-rays as being an 

 expression of the fundamental segmentation of the trunk, accessory to 

 it no doubt, but still of the same nature and histologically dependent 

 upon it. The extension of this repetition along the morphological side 

 of the face is thus an anomaly. 



Further comment on the nature of the variation will be made 

 after the chief cases have been given. 



*727. Rhombus maxirnus (Turbot). Two specimens respectively 9 in. 

 9 lines and 7 in. G linos in length, 7 in. 6 lines, and 5 in. 6 lines broad. 

 Both sides of a similar coffee-brown colour. The smaller had a 

 yellowish white spot, about 1 in. square, on the operculum of the lower 

 side. The colour was more uniform than usual and the dark spots 

 normally found on the fins of the Turbot were absent. Both sides 

 irregularly beset with horny tubercles, only slightly more developed on 

 the upper than on the lower sides. Fine scales were also found deep 

 in the skin of both sides. All fins except the dorsal were normal in 

 form and position. The dorsal fin was anteriorly detached from the 

 head, being borne on a horn-like projection. The separation between 

 the head and dorsal fin was continued backwards as a semi-circular 

 notch to a level behind the eyes. Upon many of the fin-rays of the 

 dorsal, anal and caudal fins there were 1 7 small knotty elevations of 

 the size of poppy-seed. In the smaller specimen these elevations were 

 smaller, and on the caudal fin absent. The left eye had its normal posi- 

 tion, but the right eye [of "blind" side] was placed on the top of the 

 head, but in such a position that it could scarcely have seen any thing 

 not directly over it. [See further details given.] SCHLEEP, I sis, 1829, 

 p. 1049, PL in. 



Similar specimen Coucn, Fishes Brit. IsL, in. p. 157. Dried speci- 

 mens in Brit. Mus., Newcastle Mus., &c. 



*728. Very good figures of such a Turbot are given by DUHAMEL DU 

 MONCEAU (Traite general des Pesches, 1777, in. Sect. IX. p. 262, PI. ill. 

 figs. 3 and -i). The under side was of nearly the same colour as the 

 upper and the tubercles generally found on the upper side only were 

 present on the lower side also, though of smaller size. A slight notch 

 separated the dorsal fin from the head; but the upper eye is figured as 

 in its normal place, not being on the top of the head, and it would of 

 course be invisible from the " blind " side. [This important case is 

 referred to by STEENSTKUP, but seems to be unknown to others, who 

 attribute the separation of the dorsal fin to the persistence of the eye on 

 the top of the head.] 



729. A young turbot, similarly coloured on both sides, having the eyes 

 still symmetrical, swimming on edge, is figured by McIxTOSH, Fishes of 

 St. Andrews, 1875, PI. vi. figs. 5 and G. Prof. Mclntosh kindly 

 informed me that these "double" individuals swim on edge much 

 longer than usual. 



730. Rhombus lacvls (Brill). Specimen presenting similar characters. The lower 

 (rt.) side of a uniform dark colour with exception of a white patch on operculum. 

 The right pectoral fin was whitish. The under side was rather darker than the 

 upper and the mottling present on the upper side was entirely absent from the 

 uuder side, which was without marking or spot. This is very probably a post- 



