112 



We fliall here alfo remark that the author oF the BritiJJj 

 Shells has confidered our antiquus as a diftinct fpecies, and 

 at the latter end of liis work defircs it may be called dupli- 

 catu.'!, a fl-;ell which he exprefsly confidcrs as diiliii^l from 

 hiscannatiis, Tab. 10^. 



If we are to be guided by thofe authors who appear to 

 "have had good opportunity of confultingthefefliells, it fiiould 

 feem there is confiderable doubt whether three out of the 

 four fliells in quefiion are not actually the fame. Upon the 

 whole there appears fo much difficulty in determining how 

 to divide thefe Ihells^which are fo clofely connei^ed by every 

 ihade of gradation, that only additional confufion would arife 

 by another divifion, until more light is thrown on the fub- 

 je6l ; but we think Mr. Donovan is right in referring to 

 the defpectiis of EngliJIj colle(5"lors for the Linnaan antiquus. 



Martini remarks that all thefe varieties are found upon 

 the fhore at Elfineur in vafl abundance, all of which he has 

 confidered as mere varieties of the Linna;aii antiquus. ¥ov 

 further information we beg leave to refer to that author's 

 arguments, and to the variety of figures given in Vol. iv^, 

 Tab. 138. 



The reafon we have not united the ulain and ridged 

 Ihells into one fpecies is, that not a fingle inflance of the lat- 

 ter has ever occurred to us, amongfl: the vafl quantity of 

 the others taken on fome parts of our coafl ^ and yet they 

 are fometimes extremely thick, ponderous, and wrinkled, 

 efpecially thofe on tlie coaft of Lincoln [liire. 



The 



