135 TELLINIDA. 
within. The foot is long, broad, flat, large, white, pointed, 
and geniculated, as in Tellina; indeed, the animal is closely 
allied to that genus; the greatest difference is im the shell, 
which, with the outward ligament of the Telline, has also a 
small internal cartilage fixed in an oblique cavity. The liver 
is dark green, placed at the summit of the dorsal line. We 
extracted the crystalline stylet and attritor, called by authors 
the tricuspid membrane. 
It inhabits, sparmgly, the coralline zone at Exmouth. 
The two following species have not occurred :-— 
S. tenuis, Montagu. 
S. tenuis, Brit. Moll. i. p. 323, pl. 17. f. 11. 
S. ivteRMep1IA? Thompson. 
S. intermedia? Brit. Moll.i. p. 319, pl. 17. f.9, 10; (animal) pl. K.f. 5. 
We very much think that the S. intermedia is nothing 
more than a variety of S. prismatica, being the result of 
climate. 
SCROBICULARIA, Schumacher. 
S. prperata, Gmelin et Philippi. 
S. piperata, Brit. Moll. 1. p. 326, pl. 15. f. 5; (animal) pl. K. f. 6. 
Mactra compressa, nonnull. 
Animal suboval, compressed, pale yellowish-brown; mantle 
open, with a frige only visible by the aid of a good lens; the 
siphons are nearly as long as the shell, separate from their 
bases, of the same length, subcylindrical, tapermg to the 
extremities, which are truncate, without cirrhi, of a pale dirty- 
brown, the effect of a fine epidermis. There is, on each side, 
a single, subangular, pale yellow branchia, running obliquely, 
I may say almost vertically, from the dorsal to the ventral 
range, very finely pectimated on the outside, but more in- 
tensely within; the ¢wo palpi, on each side, are large, thin, 
flat, very long, triangular, broad above, pointed at their ter- 
minations ; they present the same characters as to colour and 
pectination as the branchice. 
This is strictly a littoral species, inhabitmg the quiet muddy 
