History of British animals - University of Guam Marine Laboratory

Pinna. MOLLUSCA. TRIGONIAD^E. 407Length 5, breadth 2 inches ; corneous, brittle, glossy.On the open sidethe contour not rounded till near the broad extremity.416. F\ papyracea. — Shell oval, triangular, with nine remoteunarmed ribs.Turt. Biv. Brit. 224. t. xx. f. 3—Coast of Devon.Length 4a, breadth 2±th inches ; thin, brittle ; the distant r&s cover nearlythe whole surface ; the anterior margin slightly rounded ; contracted rapidlytowards the apex the ; open end even.EXTINCT SPECIES*1. P. affinis Cuneiform, ventricose, straight, longitudinally ribbed, ratherthick, smooth.— Sower. Min. Conch, t. 313. f. 2.—London Clay.2.' P. arcuata.— Nearly equilateral, ventricose, finely ribbed, arched. — Sower.Min. Conch, t. 313. f. 3—London Clay.3. P. lanceolata—Lanceolate, slightly curved, longitudinally striated, seclionSower. Min. Conch, t. 281.— Inferior quadrangular.— Oolite.4. P. tetragona.—Narrow, smooth, or obscurely ribbed, prismatic ; valveslongitudinally carinated with a suture in the middle.—Sower. Min. Conch.t. 313. f. I.—-Green Sand and Oolite.5. P. granulata.— Broad, nearly equilateral, convex, obscurely decussated,with a small elevation in the centre of each division ; anterior side rounded.Sower. Min. Conch, t. 347—Oolite.6. "P.jlabelliformis.—Somewhat fan-shaped, beaks pointed ; broad end round"ed ; surface with narrow longitudinal ribs, and broad, shallow, smooth fur.rows—Mart. Derb. t. vi. f. 1, 2.— Carboniferous Limestone.