History of British animals - University of Guam Marine Laboratory

404 MOLLUSCA. TRIGONIADtE. Tuigonia.trigoniam:.Gen. TRIGONIA.— Equivalve, unequilateral trigonal; onthe rightvalve are two oblong, flat, diverging hinge teeth,transversely grooved on each side ;on the left valve fourflat hinge teeth, transversely grooved on one side only, disposedin pairs ;ligament external, marginal.1. T. costata Triangular, with transverse, smooth ribs ;anterior sidemarked with many small, and three large, prominent, longitudinal,crenulatedridges Curvirostra rugosa,Luid. Lith. 36, t. ix. f. 714 —T. cost. Park.Org. Rem. iii. 175, t. xii. f. 4 Sower. Min. Conch, t. lxxxv.— Inferior Oolite.2. T. spinosa Roundish, depressed, many ribbed ;anterior side truncatedribs ; oblique, diverging both ways from the ridge that separates the anteriorside ;set with short spines.— Park. Org. Hem. iii. 177- t. xii. f. 7-—Sower. Min. Conch, t. lxxxvi.— In Green Sand.3. T. clavellata Triangular, rather wider than long, with ten or more ohliquerows of tubercles ;anterior side straight, with three longitudinalknottedridgesLuid. Lith. 36, t. ix. f. 107- Park. Org. Rem. iii. 175- t. xii.f. 3. Sower. Min. Conch, t. lxxxvii.— Oolitic Series.4. T. dasdalea.—Obtusely rhomboidal, with many oblique rows of tubercles ;anterior side angular,with many scattered tubercles, and one longitudinalrow bounded by a longitudinal ridge, on which is another row of large tubercles.—Park,Org. Rem. iii. 176, t. xii. f. 6. Sower. Min. Conch, t. lxxxviii.— Green Sand.5. T. eccentrka Transversely ovate, convex ; anterior side produced.posterior side round, with oblique undulating ridges on the surface.— Park.Org. Rem. iii. 175, t. xii. £ 5—Sower. Min. Conch, t. ccviii. f. 1, 2—InGreen Sand.G. T. affinis Transverse, oval, gibbose, half covered by transverse ridges.—Sower. Min. Conch, t. ccviii. f. 3—Green Sand.7. T. aliformis.—"Wing-formed;anterior side produced, truncated, with abroad compressed ridge extended to the beak ; posterior side costated, rounded; costte many, thick, irregularly crenulated, oblique, recurved, and attenuatedtowards the ridge on the anterior side, where they terminate—Park.Org. Rem. iii. 176, t. xii. f. 9. Sower. Min. Conch, t. ccxv—In Green Sand.8. T. gibbosa Transversely oblong, gibbose, slightly arched, concentricallyundulated, or irregularlysulcated ;anterior side separated by a broadlongitudinal furrow or plane Min. Conch, t. ccxxxv. ccxxxvi.space—Soiver.Upper Oolite.9. T. striata Obtusely triangular, convex ;with arched, oblique, crenulatedcostse upon the middle and posterior side ;anterior side nearly coveredby numerous, elevated, sharp Min. Conch, t. ccxxxvii.ridges—Soiver. f. 1, 2,3.— InferiorOolite.10. T. duplicata.—Transversely oblong ; anterior side marked with smallundulating ridges, and bounded by a strong tuberculated ridgeover the;middle are longitudinal crenulated costae, suddenly reflected over the posteriorside ;on the front are short intermediate ridges.— Sower. Mm. Conch.t. ccxxxvii. f. 4, 5.— Inferior Oolite.