406 Mr. W. Thompson on the British Species of 



one-seventh the length of head ; scales on lateral line about 

 70 ; an occasional black ray throughout the dorsal and anal 

 fins, this colour not spreading over the adjoining membrane. 



Thus far all seems clear, the British specimens recorded 

 being allocated under the two species just treated of, with the 

 exception of Hanmer's Red-backed Flounder obtained at 

 Plymouth, and Montagu's specimen from the same locality. 

 All that is wanted to fix the species of the first-mentioned is 

 an examination of a moderate-sized Man. variegatus. This 

 Mr. Yarrell possesses ; and now supplying him with the spe- 

 cimens by which I arrived at the above conclusions, I leave 

 this point to be determined in the forthcoming Supplement 

 to his ' History of British Fishes.' As all the British Mono- 

 chiri and Solece are taken on the southern coast of England, 

 it signifies little to which of the species Montagu's specimen 

 belonged. 



It may not be useless to mention some of the comparative 

 differences between Hanmer's Red-backed Flounder, (of which 

 two specimens, procured by Dr. Parnell at Brixham*, are 

 now before me,) the Mon. linguatulus and Mon. variegatus. 

 From the M. linguatulus it is at once seen to be specifically 

 different, by the greater length of its pectoral fin, (about ^ 

 that of head, whereas it is about one-seventh in the other,) 

 by its smaller scales (about 85 in the lateral line, the other 

 having about 70), and by the conspicuous blotches of black, 

 of which part is on the dorsal and anal fins, and part on the 

 body of the specimens f. With M, variegatus the Red-backed 

 Flounder accords in the length of pectoral fins, the number 

 of scales on the lateral line, and in general form ; in every 

 character indeed, so far as I can judge from comparison with 

 a specimen of M. variegatus under three inches in length, ex- 

 cept in colour. This difference, in itself certainly not specific, 

 is nevertheless very striking ; my specimen of M. variegatus, 

 2| inches long, Mr. Yarrell's 5 inches, and Donovan's 9 inches 



• It was between these or similar specimens that Dr. Parnell, calling 

 them Mon. Lingula, clearly showed the characters in which they differed 

 from his Mon. minutus. See Mag. of Zool. and Bot., vol. i. p. 528. 



f The black spots mentioned in my description of the colours of Sol, Lin- 

 gula, Rond. (Annals, loc. ciL), differ entirely from these by appearing on 

 the body only ; they are small roundish spots, generally about a line in dia- 

 meter. 



