Pvn H,i I'UitlS

TAPES. 359
pied the former burrow of a Pholas dactylus,
has a
group of Serpula triquetra attached to it on the poste-
rior side, the hole being large enough to contain both.
This is a confirmatory proof that T. pullastra does not
perforate any hard substance.
Although Mr. William Wood figured this species in
the ' Linnean Transactions '
(vol. vi. 1. 17. f. 13, 14), and
showed that the structure of its hinge was different from
that in T. decussatus, he did not assign any specific name
to it. I believe our shell is the Venus literata of Linne
and Poli ; but that name is now used for a tropical species.
As I have before remarked, the V.geographica of
Chemnitz is the southern form or variety, to which the
V. eremita of Brocchi, V. bicolor, V. catenifera, V. retifera,
and Veneriipis nucleus of Lamarck, and the Venus
Tenorii of Costa may also be referred.
4. T. decussa'tus *, Linne.
Venus decussate, Linn. Syst. Nat. p. 1135 (according to modern authors).
T. decussaia, F. & H. i. p. 379, pi.
xxv. f. 1.
Body thick, oval, very pale cream- colour or greyish-white ;
with white :
margins having their edges scalloped or fringed
tubes subcylindrical, separate throughout, and (at the will of
the animal) diverging in various directions, of the same length,
which when they are extended is equal to the breadth or
transverse admeasurement of the shell; they are at times
greatly distended ; their colour, to within a quarter of an inch
from the orifices, is pale yellowish-white, interspersed with
minute flakes of pure white, streaked or speckled near the
orifices with confused tawnv-vellow, reddish-, or dark-brown
markings ; orifices encircled with cirri, that of the lower (or
alimentary tube) having about 12 long and as many alternate
shorter ones, and the upper (or excretal) tube being furnished
with about 20 equal-sized ones ; these cirri are of a brown or
bistre colour :
gills suboval, pale brown sprinkled with minute
darker points ; as usual, the upper pair is the smaller ; they
* Intersected bv lines crosswise.