116 



MOLLUSCA. 



[TUBICOLARIA. 



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. 



Family XI — Tubicolaria. 



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 Linnaeus. 



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. Teredo navalis, pi. L, f. 1, 1, 2, 3, 4, 5, 6, 7. 



Teredo navalis, First Ed., pi. 3, f. 1 ; Montagu, p. 527 ; lb., 

 Sup., p. 7; Donovan, V, pi. 145; Turton, Biv., p. 14, pi. 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 

 septac, 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 concamcrated structure. 



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 hipennata, Turton, Biv., p. 15 ; lb., Conch. Diet., 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, pi. L, f. 14, 15. 



Teredo nana, Turton, Biv., p. 16, pi. 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. Teredo maleolus, pi. L, f. 16. 



Teredo maleolus, Turton, Biv., p. 255, pi. 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 — Gastroch^na Spongier. 



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. Gastroch^ena Pholadia, pi. XLVIII, f. 13, 14. 



Gastrocluena modiolina, First Ed., pi. 9, f- 13, 14; Mi/a 

 Pholadia, Montagu, p. 28 and 559; lb., Sup., p. 20; Mi/a 

 dubia, Pennant, IV, p. 82, pi. 44, f. 19; Donovan, III, pi. 108; 

 Turton, Biv., p. 18; Gastrochirna Mans, Fleming, p. 458; Gas- 

 trochcena cuneiformis, Spengler, II, p. 179, f. 8, 9, 10, 11. 



