MARSHALL : ADDITIONS YO “ BRITISH CONCHOLOGY.” 3093 
Venerupis irus L.—Guernsey, rare; Scilly, rare ; Vatersay 
Sound, Barra, 5 f., a valve. 
There are three principal forms of growth — one, 
occupying the deserted burrows of Saxicava rugosa var. 
pholadis, which are very broad, cylindrical, and regular in 
shape ; the second occupy, and fit themselves into, all 
sorts of cavities and indentations, and are consequently 
of the most varied shapes, round, quadrate, triangular, 
depressed, globose, &c.; the third is a handsome shell, 
attains a large size, and lives attached by a byssus either 
to chinks in the rocks or nestling in the deserted valves of 
Pholas dactylus. It is the latter form which is figured as 
the type in various works. 
Petricola pholadiformis Lam.—-This is another American 
importation, which seems to have gained a substantial foot- 
ing on the British coasts, several naturalists having taken 
specimens on our southern shores. Mr. A. S. Kennard, of 
Beckenham, to whose kindness I am indebted for specimens, 
‘writes me that the latter were taken at Herne Bay, “just 
above low-water mark, where it is rather common though 
somewhat difficult to obtain.” Jeffreys has recorded it 
from ‘‘ Valentia, Ireland; a fragment,”! presumably from 
the Porcupine Expedition of 1869; but as he did not 
further notice it in his report of that expedition, it may 
either have been an error or a fragment too trivial to men- 
tion. See also a note by Mr. J. E. Cooper, with a figure, 
in Science Gossip, 1896, p. 147. 
Gastrochzna dubia Penn. — Low water to 20f. Scilly 
(Smart and others) ; Torbay, in new red sandstone, at low 
water, associated with Pholadidea. Their burrows here are 
beautifully enamelled like porcelain, and remarkably solid. 
Weymouth and Babbacombe Bays, at low water of spring 
tides, in limestone. 
Var. ovalis Jeff.—Torbay, with the type. 
r Moll. Eur. and East. N. America, dun. and Mag. Nat. LHist. (4) x., 1872, p. 329. 
