474 Mr. J. Alder on Sepia biserialis and Sepia elegans. 



XXXVII, — Notes on Sepia biserialis and Sepia elegans. 

 By J. Alder. 



To the Editors of the Annals of Natural History. 



Gentlemen, 



In a paper communicated to the Linnsean Society, and published 

 in the 3rd Part of their ' Proceedings/ Mr. Couch announces his 

 having found ten specimens of the dorsal plate or bone of Sepia 

 biserialis on the Cornish coast. On a careful perusal of his 

 description, however, I am inclined to think that Mr. Couch 

 has mistaken the species, and that the plates he found belong 

 to Sepia elegans, Blainv., a species not before known to be 

 British. 



Sepia biserialis is a small species, the bone of which does not 

 exceed 2^ inches in length, but 2 inches is the more general 

 size. It tapers gradually to a point below, where it is much 

 curved inwards (as may be seen in pi. P P P. fig. 2c of ' British 

 Mollusca ^), and has no spur, but only a slight keel or ridge at 

 that extremity. S. elegans is considerably larger: its dorsal 

 plate is usually 3^ inches long; it is more ovate in form than 

 that of S. biserialis (though less so than in >Si. officinalis), and is 

 distinguished by the very strong spur, which is a little com- 

 pressed laterally, so as to form a slight ridge before and behind : 

 the plate is not so much curved inwards below as in the former 

 species. This agrees with the description of Mr. Couch. Professor 

 Edward Forbes has suggested that these may be only different 

 sexes of the same species; but this opinion, I suspect, was 

 hazarded without having seen specimens, an inspection of which 

 would, I think, have led to a different conclusion. Professor 

 Verany has kindly sent me specimens of both kinds from the 

 Mediterranean. 



There can be little doubt that the Cuttle-fishes whose dorsal 

 plates are cast up on our shores from time to time are indige- 

 nous. With respect to S. biserialis, its title to be considered 

 British does not rest solely on the evidence of dorsal plates cast 

 on shore, as the specimen from which the description and figures 

 in the ' British Mollusca^ were taken, was extracted by myself 

 from the stomach of a cod at Cullercoats, with the animal nearly 

 entire, but too much decomposed for preservation. 



I am. Gentlemen, 



Yours very truly, 



Joshua Alder. 



Newcastle-on-Tyne, May 1857. 



