116 
lance-shaped, longitudinal plate, joined to the membrane by 
which the valves are connected, extending to nearly the pos- 
terior extremity; the basal margin is provided with an elon- 
gated, testaceous, accessory plate, which seems to prevent the 
valves from opening, except at the extremities; inside smooth, 
white, with a short, longitudinal, rounded rib, becoming more 
developed as it approaches the base, crossed by rough points. 
General length half an inch; breadth three-quarters. 
Found on the Devonshire coast, burrowing in a piece of 
rotten wood, and Dr. Turton found it in an old yard-arm of a 
vessel drifted ashore at Brixham. The Pholades always per- 
forate the wood across the grain, while the Teredo navalis 
penetrates the wood with the grain. 
Famity XI.—Tusicovaria. 
Shell contained in a testaceous sheath, distinct from its 
valves, incrusted entirely or in part in the wall of this tube, or 
projecting outwards. 
Genus 48.—TEREDO.— Linnzus. 
Shell equivalve, inequilateral, and orbicular, with a subulate 
process in front, and gaping at both sides; anterior opening 
angular at the back, and the posterior one rounded in front ; 
an elongated, curved, tooth-like process emanates from the 
inside, in both valves, protruding from the umbones; anterior 
muscular impression situate upon the subulate process; this 
shell is placed on the anterior extremity of a testaceous, acces- 
sory tube, which is secreted by the animal in its progress 
through wood, and forms a lining to the perforated cavity, 
becoming gradually wider as the animal advances, and is fre- 
quently furnished internally with vaulted septa; aperture of 
the tube round, and posteriorly divided into a double tube, 
which the animal has the power of closing by means of two 
palmate, sometimes pennated opercula. 
1. TrrEpo navaus, pl. L, f. 1, 1, 2, 3, 4, 5, 6, 7. 
Teredo navalis, First Ed., pl. 3, f. 1; Montagu, p. 527; Ib., 
Sup., p- 7; Donovan, V, pl. 145; Turton, Biv., p. 14, pl. 2, f. 
1, 2,3; Fleming, p. 554. 
Shell with the valves triangular, ear-shaped behind, and 
hemispherical when closed; one valve with a curved denticle 
on the margin at the umbonal region; surface of the valves 
striated in various directions, each with a triangular projection 
in front, inclining a little inwards, and conforming to the angu- 
lar form of the valves, with a lengthened, flat, curved tooth, 
projecting inwards under the hinge, in the same manner as the 
Pholades; this bivalve is seated on the wider end of a thin, 
white, flexuous, brittle, nearly circular, and rather abruptly 
tapering tube, which is internally provided with transverse 
septe, reaching half way across the tube; inside of the valves 
white; the supplemental valves seated on the inside of the tube, 
and near the smaller end are spatuliform, being convex exter- 
nally, and concave internally; one end linear, elongated, and 
straight, the other truncated. 
Fig. 1 b represents a section of the lower end of the tube, 
shewing the concamerated structure. 
MOLLUSCA. 
[Tusrconaris. 
Fig. 2 is an entire tube, shewing the bivalve seated on its 
wider extremity a. 
Fig. 3, 4, 5, different views of the bivalve. 
Fig. 6, 7, different views of the spoon-shaped appendages, or 
opercules. 
2. TEREDO BIPENNATA. 
Teredo bipennata, Turton, Biv, p. 15; Ib., Conch. Dict., p. 
184, f. 38, 39, 40; Fleming, p. 454. 
Shell with the valves ear-shaped behind, and the auricles 
reflected; an oblique rib on the margin, above the teeth; some- 
what larger than the last; tube thicker, stronger, and destitute 
of the internal concamerated partitions; and instead of the 
spoon-shaped valves, provided with two very long, slender ap- 
pendages, somewhat curved and feathered on each side. 
Found in drifted timber at Exmouth. 
3. TEREDO NANA, pl. L, f. 14, 15. 
Teredo nana, Turton, Biv., p. 16, pl. 2, f.6, 7; Fleming, p. 
455. 
Shell with rounded valves, and destitute of auricles behind; 
a strong, conic, oblique tooth on the margin, at the umbo; 
valves destitute of a jointed, internal, longitudinal rib. Dia- 
meter not quite an eighth of an inch. 
Found burrowing in a piece of wood at Torbay. 
4. TrEREDO MALEOLts, pl. L, f. 16. 
Teredo maleolus, Turton, Biv., p. 255, pl. 2, f. 19; Fleming, 
p- 455. 
- Shell with ear-shaped valves behind, detached on their inter- 
nal edge, with reflected auricles; accessorial valves mallet- 
shaped, and placed transversely; anterior triangular processes 
remotely striated, and few in number; tube consisting of a 
light calcareous deposit on the surface of the chamber, with its 
termination slightly semiconcamerated ; accessorial valves ter- 
minal. Diameter a quarter of an inch. 
Found in rotten wood at Torquay. 
Genus 49.—GasTRocHENA.—Spengler. 
Shell equivalve, inequilateral, somewhat wedge-shaped; ante- 
rior side rounded, when viewed in front, posteriorly acumi- 
nated, and gaping widely, its aperture being subovate, and 
acute behind; hinge marginal and linear, destitute of teeth, 
but in their stead a small laminated appendage, emanating from 
the umbo, allied to the same tooth-like process in the genus 
Pholas ; ligament external. 
This shell is enclosed in a testaceous, irregular, claviform 
tube, situate at its broader extremity; it is open and attenuated 
anteriorly, with an oblong, bilobate aperture, which is nearly 
subdivided by a projecting septum that does not quite reach 
across the opening; these serve for the passage of the two 
tubes of the animal; the posterior end of the tube is closed. 
This club-shaped tube is found either within the perforated 
cavities of rocks, or in old shells or corals, the testaceous tube 
always protruding beyond the surface. 
1. GastrocHzna Puoxapia, pl. XLVIII, f. 13, 14. 
Gastrochena modiolina, First Ed., pl. 9, f. 13, 14; Mya 
Pholadia, Montagu, p. 28 and 559; Ib., Sup., p. 20; Mya 
dubia, Pennant, IV, p. 82, pl. 44, f. 19; Donovan, III, pl. 108; 
Turton, Biv., p. 18; Gastrochena hians, Fleming, p. 4583 Gas- 
trochena cuneiformis, Spengler, II, p. 179, f. 8, 9, 10, 11. 
