MARSHALL: ADDITIONS TO “ BRITISH CONCHOLOGY.” 357 
as long, and should be measured accordingly. The surest 
guide in separating this from C. echimatum is that in the 
latter the rows of spines are continuous, while the spines 
in C. tuberculatum have spaces between. 
There is a long, narrow, and more convex form, corre- 
sponding to C. echinatum var. ovata, occasionally found in 
various parts of South Devon. The monstrous valve noted 
in ‘ British Conchology,” from the Turton Collection, has 
occurred to me several times in South Devon. 
C. papillosum Poli.—Low water to 20 f. Herm, a live speci- 
men from low water ; Scilly, 40f., a fresh valve ; Falmouth 
Harbour, 19 f., another fresh valve. 
C. exiguum Gm.—The very young and fry resemble the same 
stage of C. nodosum; but in the former the sculpture is 
coarser, and in the latter the posterior side is not truncate 
but rounded. It is abundant and fine off Trefusis Point, 
Falmouth ; and equally abundant, but small, in Milford 
Haven. 
Var. subquadrata Jeff.—Sutherlandshire (Baillie) ! Herm, 
low water ; Guernsey, 20 f. This is less gibbous than the 
type, but the sculpture of the furrows is similar. 
C. fasciatum Mont.—This is the most variable of all this 
genus. Some are broader than long, and wece versa. 
Jeffreys’ figure is the type ; Sowerby’s is too triangular. 
The very young are less square than those of C. exiguum, 
and have sharp and prominent beaks ; the ribs are more 
numerous and smooth, with only a few tubercles at the 
sides. They are not ‘‘almost flat.” Jeffreys’ dimensions 
of half an inch in length and breadth are extreme; the 
largest are 4 lines by 44. 
Var. globosa Jeff.—Sutherlandshire (Baillie)! ; off Aber- 
deen, 50 f. (‘Triton’)!; Loch Boisdale, 35 f. 
Var. alba Jeff.—Sutherlandshire (Baillie) ! ; Scilly Islands. 
C. nodosum. 
ground in St. Aubin’s Bay, Jersey, and at Herm Island ; 
Low water to 145 f. Gregarious in oozy 
