7G INIOLLUSCA FROM THE CRAG. 



1. Arca tetragona, Poll. Tab. X, fig. \,a — d. 



AucA TETKAGONA. PoU. Test. Sic, vol. ii, p. 137, pi. 25, figs. 12, 13, 1793. 



— — Turt. Brit. Biv., p. 1C6, pi. 13, fig. 1, 1822. 



— — Payr. Cat. Moll. Cors., p. 61, No. 105, 1826. 

 - — Desk. 2(1 ed. Lam., t. vi, p. 461, 1835. 



— — Forbes. Malac. Mouen., p. 41, pi. 3, 1838. 



— — Id. Report on iEgcan Invert., p. 181, 1843. 



— — Phil. En. Moll. .Sic, vol. i, p. 57, 1836. 



— — Reeve. Conch. Icon. Monog. Area, pi. 15, fig. 100, a — b. 



— — ? Menke. Moll. Nov. HoU. p. 37, No. 208, 1843. 



— No^. Mont. Test. Brit., p. 139, pi. 4, fig. 3, 1803. 



— — Don. Brit. Shells, vol. v, pi. 158, figs. 1, 2, 1804. 



— — Brown. Brit. Conch. lUust., pi. 25, figs. 1-3, 1825. 



— — S. Wood. An. and Mag. Nat. Hist., vol. iv. New Series, p. 231, pi. 13, figs. 2, 



& 2rt, 1840. 



— — Morris. Cat. of Brit. Foss., p. 78, 1843. 



— FisCA. Mont. Test. Brit. Sup., p. 51, 1808 (not Reeve). 



— — W. Wood. Ind. Test., p. 45, pi. 9, fig. 14, 1825. 



— — Flein. Brit. An., p. 397, 1828. 



— — Thorpe. Brit. Mar. Conch., p. 101, 1844. 



— CARDISSA. Desk. 2d ed. Lara., t. \\, p. 463, 1835. 



— — Alder. Cat. Moll. North, and Durh., p. 79, 1848. 



— NAVicULARis. Desk. 2d cd. Lam., t. vi, p. 462, 1835. 



— — Phil. En. Moll. Sic, vol. ii, p. 42, 1844. 



— — Lovin. Ind. Moll. Seand., p. 33, 1846. 



— Britannica. Reeve. Conch. Icon. Monog. Arca, pi. 15, fig. 98. 



— — Nyst. Tab. Syn. des Arches. Viv. et Foss., p. 14, No. 4 7, 1847. 



— PAPILLOSA. Smith. Mem. Wern Soc, vol. viii, pi. 1, fig. 19, 1838. 

 Balanus Bellonii. List. Hist. Conch., lib. iii, fig. 207, 1687. 



Ency. Meth., pi. 308, fig. 3, a—b. 



Spec. Char. Testa oblongd, valde inaqidlaterd, costato-striatd, et transversim 

 decussatd, antice rotundatu, jmstica angulatd ; carina posticd eminente, acuta ; apicibus 

 remQtis incurvis ; marline ventrali hianie. 



Shell oblong, very inequilateral, with costated striae, decussated by distinct lines 

 of growth ; anterior side rounded, posterior angulatcd, with a prominent keel or 

 ridge from the umbo to the ])osterior ventral margin ; umbones distant, incurved ; 

 ventral margin gaping. 



Largest diameter, 1 inch. 



Locality. Cor. Crag, Sutton, Rarasholt, and Sudbourn. 



Red Crag, Sutton. Recent, Scandinavia, Britain, and Mediterranean. 



Very small specimens are by no means rare in the Coralline Crag ; but I have met 

 with Very few examples of the adult shell. These small or young specimens are very 

 regular in form, being much elongated transversely, of a somewhat rhom])oidal shape, 

 the anterior side slopes a little from the extremity of the hinge line, rounding at the 

 ventral margin, while the posterior side is angular, pointed and projecting ; the ventral 



