204 MTTILID^. 



thickness. Similar rib-like slrite adorn the anterior com- 

 mencement of the shell ; the intermediate area is apparently 

 smooth, but when highly magnified, displays an elegant 

 chasing of minute and often interrupted concentric wave- 

 like corrugations. The interior is subnacreous white, with 

 a somewhat livid cast ; the margin is not crenulated in the 

 middle, but in aged and large examples becomes not unfre- 

 quently subgranular near the beaks. An individual, which 

 we regard as rather large for a British specimen, measures 

 three-quarters of an inch in breadth, and an inch and three- 

 tenths in length. Our Newfoundland examples are at 

 least two inches in length, and full half that breadth ; and 

 both Dr. Fleming and Mr. Barlee state that British indi- 

 viduals of two inches in length are occasionally to be met 

 with. 



The animal of this species has been observed by Mr. 

 Alder, who kindly communicated the drawing from which 

 we have taken our figure. It is of a transparent white 

 hue, with the margin of the cloak and syphon tinged with 

 pink, and speckled with brown and opaque wdiite. 



This rare and fine shell is of boreal origin, and in Britain 

 occurs only in northern habitats. It has long been known 

 in the Frith of Forth, where we have dredged it on the 

 oyster-beds in seven fathoms ; and in a MS. note of 

 Captain Laskey's it is remarked that this species was 

 originally much more plentiful there than latterly, the 

 numbers having been diminished by the avidity with which 

 it was sought after by fishermen, on account of the ready 

 sale they found for specimens. In England it is only known 

 from the North Eastern coast, where it has been taken at 

 Cullercoats by Mr. Alder, who also enumerates among its 

 localities " Whitburn (Eev. G. C. Abbes). Mr. Howse 

 dredged it alive in seventeen fathoms. Mr. King has also 



