History of British animals - University of Guam Marine Laboratory

Teeebeatula. MOLLUSC A. ACEPHALA. 369Length nearly an inch and a quarter breadth one ;inch, convex, of a blackishhorn-colour ;sides abruptly turned in, and flattened, and marked with afew irregular striae front ; margin a little indented on each side, and projectingin the middle ; perforation somewhat triangular.368. T. aurita.— Regularly ribbed ; the large valve broadestin the middle, semicircular in front, and becoming narrow at theapex.Flem. Phil. Zool. ii. 493. t. iv. f. 5—T. costata, Lowe, Zool. Journ. ii.105. t. v. f. 8, 9.—West coast of Scotland.Length about T%ths, breadth T 2 5 t:hs of an inch ;whitish ; the ribs, from thebeak to the margin, the most distinct, rounded, and about eight in number,obsoletely wrinkled concentrically the ; ribs, towards the sides, indistinct ;margin crenulated by the ribs ;the small valve nearly orbicular ;the hingemargin subtruncated, or rather obtusely angular, and having the sides depressedinner surface punctated ; ; peduncle short, of numerous unequal andtubular threads attached to a complicated tendino-muscular apparatus, andchiefly to the lower valve. I obtained a small specimen of this species atUllapool, in Loch Broom. The one, of a larger size, described by Mr Lowe,was found by Mr J. Berkely, at Oban.EXTINCT SPECIES.* Margin of the valves entire, or slightly icaved.1. T. subrotunda Circular, depressed, smooth ; valves regularly and equallyconvex. —Sower. Min. Conch, t. xv. f. 1, 2 In Chalk.2. T. ovata.—Ovate or oblong-ovate, depressed, smooth ; small valve flatfish,slightly pentangular—Sower. Min. Conch, t. xv. f. 3—In Green Sand.3. T. punctata Oblong, depressed; valves equally convex ;edge straightenedat the front ;the whole surface finely punctated — Sower. Min. Conch.t. xv. f. 4—In Lias.4. T. carnea.— Depressed, smooth, obtusely five-sided front ;edge short ;valves equally convex, slightly flattened along the middle—Sower. Min.Conch, t. xv. f. 5, 6—In Chalk,5. T. subundata Nearly circular, depressed, smooth ; valves equally gibbousfront ; margin straight or slightly depressed in the middle, with one undulationon each side of it—Sower. Min. Conch, t. xv. f, 7—In Chalk.G. T. intermedia Obscurely five-sided, rather depressed, smooth ;largervalve most convex ; front margin undulated ; three depressions in the smallervalve, and two in the larger.— Sower. Min. Conch, t. xv. f. 8.— Green Sand.7. T. scmiglobosa Nearly circular, gibbous, smooth ; largest valve deepest,and uniformly gibbous; front margin undulated, with two risings in thesmaller valve Sower. Min. Conch, t. xv. f. 9—In Chalk.8. T. biplicata.— Oblong, gibbous; beak prominent ; sides rounded ; frontstraightish when full grown, elevated with two distant large plaits— Soivcr.Min. Conch, t. xc. and t. ccccxxxvii. f. 2, 3—In Green Sand.9. T. digona.— Triangular, oblong, gibbous beak ; prominent; sides rounded;- front either convex or concave ;when old, bounded by two prominentangles, alike in each valve.— Sower. Min. Conch, t. xcvi.— Oolite.10. T. ovoides.—Ovate, elongated beak prominent ; ; larger valve gibbous,VOL. I.a a