MARSHALL : ADDITIONS ‘10 “ BRITISH CONCHOLCGY.” 391 
The shell frequently wants the concentric plaits or 
folds (Jeffreys). 
N. costellata Desh.—12 to 70 fathoms. Loch Fyne, oppo- 
site) themoldcastie-scamllash, 15| i) Manbent, 20-200 : 
Brodick Bay, 40 f. 
N. cuspidata Olivi._—r2 to go fathoms. Catacol Bay, 25 f., 
Lochranza, 30f., and Brodick Bay, in Arran, 20—,0 f. ; 
Gairloch, 30 f.; Sound of Sleat, 60—9g0 f.; off the West 
of Small Cumbrae, 65 f. (Somerville and J.T.M.); Loch 
Linnhe, 24 -f. (Knight)!; Doggerbank, 75 miles off Scar- 
borough, 35 f. ; Loch Fyne, 30 f. 
Var. curta Jeff.—Doggerbank, 35 f. 
Var. cinerea Jeff.—East Shetlands, 40 f. 
N. rostrata Spengl.—Feerce Channel (Triton). 
The Feerce Channel has also yielded WV. obesa Lovén, 
a Norwegian species. 
Corbula gibba Olivi.—I have a monstrosity from the 
Hebrides in which the posterior end is abnormally pro- 
duced, like the rostral beak in Veera. 
Mya arenaria 1..—Drumbeg, Sutherlandshire, very fine, 5 in. 
by 3in. I have examples of a small stunted form which 
were taken from sand being used for building purposes in 
Great Russell Street, London, near the British Museum, 
and which were still alive ! 
M. truncata L.—-The young and fry afford another instance 
in which the shells differ markedly from those of the adult. 
M. binghami Turt.—- Weymouth Bay, in soft sandstone. 
From the very young of JZ. truncata it differs in the latter 
being more regularly oblong. The published figures of this 
species apply to that form only which lives free and unen- 
cumbered in the deserted galleries of Saxicave. But 
numerous individuals will be found in stones, weeds, &c., in 
which the shell is not conformable to any particular shape, 
and these give some trouble in separating from Sax7cava 
rugosa on the one hand and 7hracia distorta on the other. 
