to 
92 MARSHALL: ADDITIONS TO “ BRITISH CONCHOLOGY.” 
Gs: 
From the former, it differs in having an internal instead of 
an external ligament; and from the latter, in the texture of 
that shell being granulated, which is always observable 
with a lens. 
Var. elongata Jeff. 
Land’s End ; Torbay. 
Panopea plicata Mont.—Mulroy Bay, Donegal (Darbishire) ; 
Largs, 20 f. (Robertson) ; Loch Gilp, Clyde, a live speci- 
men (A.. Brown); Brora (Baillie)! Loch Long, 24 f. 
(Knight)! Gairloch, 30 f., and Vatersay Sound, 5 f. (Somer- 
ville and J.T.M.) ; off Scarborough (Jeffreys), an imperfect 
valve; Knapdale Lochs; Loch Swin; Kyles of Bute; 
Aberdovey, N. Wales; Doggerbank. Also Corea, 40 f., a 
small valve, but unmistakeable (H.M.S. Sylvia). 
Saxicava norvegica Speng.—Moray Frith, a valve (coll. 
Edwards) ; Aberdeen trawl boat, one specimen (Dow). 
S. rugosa var. cylindrica S. Wood (J. of C., vol. vii., p. 248). 
—Dornoch Frith; west coast of Ireland. 
The variety precisa is generally diffused, and var. pho- 
fadis is abundant wherever there is siliceous limestone. 
Var. precisa differs from Aya binghami, which it often 
closely resembles, in the posterior angle being still more 
abruptly truncated, and especially in the external ligament. 
In AZ. binghami the beaks are also more acute and closely 
interlocked. <A figure of the var. pholadis will be found in 
Brit. Moll., iv., pl. vi., fig. 8. : 
The dimensions given by Jeffreys for the type are very 
unusual. An inch in breadth by half-an-inch in length is 
the usual size. The position of the beaks is extremely 
variable, and the shell is sometimes considerably inequi- 
valve. A monstrosity taken from a lump of limestone 
dredged in the British Channel by Mr. Bartlet Span has 
the posterior end extended into a prolonged and upturned 
beak, similar to a monstrosity of Corbula gibba previously 
noticed. 
J.C., vin., July 1867 
