342 CRETACEOUS LAMELLIBRANCHIA. 



In this work Exogyra is retained as a genus since the species dealt with seem to 

 be genetically related, but it is probable that the exogyriform type has originated 

 independently in some earlier deiDOsits. It is even possible that a few species 

 referred to Ostrea may have arisen from an exogyriform type by the increase in the 

 size of the attached surface, and the gradual loss of the spiral character of the 

 umbo. 



In the Ostreidpe, perhaps even more than in the case of hioceramns, the number 

 of figures which can be given is altogether insufficient to convey an adequate idea 

 of the great variability of the species. It is only by the study of very extensive 

 collections of specimens that one can hope to arrive at satisfactory conclusions. 



Genus — Ostkea, Linnseus, 1758. 

 (' Sjst. Nat.,' eJ. 10, p. 696.) 



Ostrea diluviana, L. Text-figures 98-138. 



1767. Ostrea diluviana, Linnxtis. Syst. Nat., ed. 12, p. 1148. 



1768. G. W. Knorr and J. E. M. Walch. Eecueil. Mon. Catastr. Petrificat., 



vol. ii, ji. 123, pi. D ii, figs. 5, 6. 

 1779. " Getphite," B. Faujas-St.-Fond. Hist. nat. Mont. St. Pierre de Maes- 



tricht, p. 151, pi. xxiv, figs. 1, 2. 

 1806. OsTEEA PECTiNATA, Lumarck. Ann. du Museum, vol. viii, j). 165 ; vol. xiv, 



1809, pi. xxiii, f. 1. 



— — CAEINATA, LamarcJc. Ibid., vol. viii, p. 166. 



1811. — FRONs, J. Parkinson. Organic Eemains, vol. iii, p. 217, pi. xv, 



fig. 4. 

 1813. OsTEACiTES PLiCATissiMtrs, E. T. V. ScJilotheim. In Leonbard's Taschenb. 



fiir Miu., vol. vii, p. 112. 

 1819. Ostrea coltjbrina, Lamarch. Anini. sans Vert., vol. vi, j). 216 {non 



Goldfuss). 



— — CAEINATA, Lamarch. Ibid., p. 216. 



— — DILUVIANA, Lamarck. Ibid., p. 214. 



1821. OsTEAciTES DiLuviANUs, G. WaMenberg. Petrific. Tellur. Suecanse, p. 58. 



1822. OaiiBEA CAEINATA, /. Sowerly. Min. Conch., vol. iv, p. 89, pi. ccclxv. 



— — — G. B. Sotverhij. Genera Eecent and Foss. Shells, No. 



vi, fig. 1. 



— — 8EREATA, G. Ciiviev and A. Brongniart. In Cuvier's Ossemens 



Fobs., vol. ii, pt. 2, pp. 251, 599, pi. iii, fig. 10. 



— — CAEINATA, Cuvier and Brongniart. Ibid., pp. 320, 599, pi. iii, 



fig. 11. 

 ' 1824. — MACEOPTEEA, J. de C. Sowerly. Miu. Conch., vol. v, p. 105, pi. 



cccclxviii, figs. 2, 3. 



