174 MR. J. T. CUNN'IlSrGHAM ON [Feb. 19 



to press upon the right half of the cerebelhim, which it had to 

 some extent excavated. This mass was enclosed m a sheath of 

 pia mater continuous with that over the posterior part of the 

 right cerebral hemisphere. Dr. Wilson thought that the spherical 

 mass might at one time have been joined to the cerebral hemi- 

 sphere, but of this there was no direct evidence. Microscopically 

 the tumovir mass contains true nerve-cells, and so is an example of 

 an extremely rare condition. 



3. On a peculiarly Abnormal Specimen o£ Turbot. 

 By J. T. Cunningham, M.A., F.Z.S. 



[Received January 23, 1907.] 

 (Plate XI.*) 



The specimen here described was sent to me by Dr. E. J. Allen, 

 Director of the Marine Biological Laboratory, Plymouth, in the 

 beginning of December 1906, with a request that I should examine 

 and describe it. With the fish was a normal specimen and two 

 letters referring to them — one from Mr. John D. Enys, the other 

 from Miss Olivia L. Fox. Mr. Enys' letter is dated Nov. 3, 1906, 

 and states that Miss Fox had then alive in a glass globe two 

 small Turbot caught on the sands at Polzeth, near the Doom Bar 

 at Padstow, on the north coast of Cornwall ; that the abnormal 

 fish was dark on the under side and white on the upper. Miss Fox's 

 letter states that she had had the fish about a month, and that the 

 upper side " was becoming pigmented " since she first obtained it. 



The specimen is 4*4 cm. in length and presents a condition 

 which, so far as I am aware, has never previously been observed 

 or described in flat-fish of any species. With respect to the 

 position of the eyes, the fish is a revei'sed specimen — that is to 

 say, both eyes are on the right side, whereas normally in Turbot 

 they are on the left. With respect to colour, on the contrary 

 the specimen partially resembles a normal Turbot. The right side 

 is almost entirely unpigmented ; the greater pai-t of the left side 

 is coloured like a normal Turbot. The pigmentation does not 

 extend uniformly over the whole of the left side, but is absent 

 from the head, and from the anterior part of the dorsal region 

 above the head. On these areas there are only a few scattered 

 black chromatophores. On the right or uncoloured side there are 

 also scattered black chromatophores rather more numerous than 

 on the left side of the head. It is important bo note that the head 

 and anterior region of the right side, although not fully pigmented, 

 have more pigment than the i-est of that side ; between the eyes 

 and around the dorsal eye pigmentation is almost complete. 



The number of dorsal fin-rays in the specimen is 65, of the 



ventral 47. The characteristic tubercles of the adult Turbot are 



not yet developed, but there are three little projections at the 



base of each of the dorsal and ventral fin-rays, and also projections 



* For explanation of tlie Plate, see p. 181. 



