65 



Since the above was prepared for the prefs the authors of 

 the Defcriptive Catalogue of Briiiflj Shells have defcribed and 

 figured this Ipecies from fpecimens taken on the coaft of 

 Cahhnefs. And we have examined a fpecimen from Scot- 

 land ^ in which the pice were very confpicuous. 



MYTILUS. 



This fpecies feems to be pretty generally diffufed through- Discrepans. 

 out this ifland ; we have found it on almofl all parts of our p. 169. 

 coafl from eaft to weft, from Lincolnfhire to Cornwall, and Tab. 26, f. 4. 

 in no inftance fo large as half an incli in breadth. In this 

 ftate of growth it is alfo not uncommon on the fands near 

 Dunbar, in JVortk Britain, but to our aftonifliment we were 

 informed by Mr, Boys and Mr. Laskey, that they had takeiv 

 feveral by dredging in the Frith of Forth, not lefs than an 

 inch and a half broad, and one in particular that a6lually 

 meafured two inches. A fpecimen of the former fize the 

 latter gentleman favoured us with, fo that we have no dif- 

 ficulty in determining it to be the fame fj)ecies, there being 

 no difference whatever, except in the colour of the epidermis^ 

 which is nearly black, and ufually decorticated at the umbo. 



This circumftance fhews how difficult it is to determine 

 the full extent of a (hell's growth, and how cautious we 

 fhould be in admitting fize alone to determine a fpecies. In 

 this place we cannot help adverting to two other fuppofed 

 fpecies of this, genus, the Modiolus and barbatus, which we 



I have 



