126 TELLINID. 
size, smooth on the outer surfaces, and on the inner striated 
with about thirty of the delicate vessels of the branchial cireu- 
lation ; the corresponding pairs of subtriangular palpi are also 
pale brown, smooth on the outside, except showing a longi- 
tudinal furrow, and pectimated within. 
These beautiful shells are frequently taken alive in the 
coralline zone at Exmouth. This animal may be placed, par 
excellence, at the head of the typical species. 
T. crassa, Montagu. 
T. crassa, Brit. Moll. i. p. 288, pl. 20. f. 1, 2. 
Animal suborbicular, lentiform ; the general ground colour 
is pale drab; mantle quite open, double-edged, finely, closely 
and conspicuously fringed, produced posteriorly mto two long 
rather slender siphons, separate from their bases, the branchial 
quite plain at its termination; the upper or anal one, which 
is apparently rather the largest in diameter, and capable of 
great inflation, has six triangular points at the orifice ; their 
ground colour is marked with two or three intenser whitish 
longitudinal lines. I am unable to state how far the tubes 
can be extended, as the animal was sent to Bath in 1851, 
wrapped in moist sea-weed, accompanied by bottles of sea- 
water, and had become partially collapsed; but I should 
think, judging from other Telline, that in the specimen exa- 
mined they would, when fully exserted, be at least 2 imches 
long. The shell was the largest I had ever seen, measuring 
transversely 24, and vertically 24 mches. The foot is the 
usual large, spatulate, thick, muscular, lmguiform appendage 
of the Telline, perfectly simple, without a trace of a groove in 
the heel. The pair of branchize on each side are subcircular, 
of very thin texture, the lower of great extent, the upper not 
half the depth of its larger fellow; both coarsely but not 
distinctly pectinated. The palpi, a pair on each side, are nar- 
row, slender, pointed, of a very elongated triangular shape, 
quite smooth externally, but well striated within. The liver 
is anterior, of a dark brownish-green ; the stomach contained 
the usual tricuspid membrane, or attritor, and the crystalline 
stylet of large size. The heart, auricles, nervous ganglia, with 
