TEREDO. 67 



Tube semi-concamerated at its narrower end ; posterior aperture 

 contracted in tlie middle. 



Plate IV, figs. 1-5. 



Teredo norvagicus, Spengler, Skrivter af Naturhistorie selskabet, (1792) vol. 



ii.pt. l,p. 102, pi. 2, f. 4,5, 6, B. 



„ navalis (not of Linnaeus, Home, nor Spengler), Montagu, Testae. Brittan. 



p. 527, and Supplement, p. 7. — Turt. Conch. Diction, p. 183. 



— TuRT. Dithyra Brit. p. 14, pi. 2, f. 1-3. — Fleming, Brit. 



Anim. p. 454. — Brit. Marine Conch, p. 28. — Brown, 111. 



Conch. G. Brit. p. 116, pi. 50, f. 3, 6, 7.— Crouch, Introd. 



Lam. Conch, pi. 2, f. 10. — Sowerby, Genera Shells. — Magaz. 



Nat. Hist. vol. ii. p. 23, f. 7.— Conch. Systemat. pi. 21,— 



Mawe, Conch, pi, 35. — Lamarck, Anim. s. Vert. ed. 2, vol. 



vi. p. 38 (not synonyms). — Gould, Invert. Massach. p. 26. — 



Gray, Philosoph, Magaz. 1827, p. 410.— Humphrey's Conch. 



pi. 10, f. 2, 3. — Sowerby, Conch. Manual, f. 48.— Hanley, 



Recent Shells, p, 3.— Dekay, New York Moll. p. 34, f. 325. 



„ Brugierij Delle Chiaje Memorie, vol. iv, pp. 28, 32, pi. 54, f. 9-12. — 



Philippi, Moll. Sicil. vol. i. p. 2, and vol. ii. p. 3. 



The united valves of the Teredines have fancifully, and 

 not inaptly, been compared to a helmet, the bodies or mid- 

 dle fang-shaped portions constituting the headpiece, the two 

 trigonal areas of the anterior side composing the crown, 

 and the posterior auricle forming a kind of rude ornament, 

 or support for the crest. 



This similitude we have adopted, not alone from its con- 

 veying the best idea of the general contour of the valves, but 

 also from its indicating the three external component parts, 

 viz. the triangular area or anterior commencement, the 

 body or central unguiform surface, and the auricle or pos- 

 terior extremity. 



The first of these is typically rather large, but varies 

 greatly in relative size, increasing usually with age at the 

 expense of the auricle, which is generally best developed in 

 individuals which have not quite attained to maturity. Its 

 base is not particularly oblique, and displays but little con- 

 vexity, being nearly, but not quite, rectilinear. The body, 



