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EOCENE MOLLUSCA. 



Ci/clas deperdita of Lamarck, to which J. Sowerby referred his specimen, is a different 

 shell, and as the specific appellation of deperdita had been applied by Lamarck to a 

 species of Cyrena, Mr. Deshayes proposed for Sowerby's shell the specific name of 

 Britannica, and I have accordingly adopted his proposition. 



15. Cyrena obovata, /. Sowerby. Tab. B, fig. 3 a — d. 



Cyolas obovata, J. Sow. Min. Conch., t. 162, figs. 5, G, 1817. 

 Cyrena — Morris. Catal. Brit. Foss., 2nd edit., p. 200, 1854. 



— (corbicula) obovata, Sandb. Land- und Sussw.-Conch., p. 2G1, t. xv, 



figs. 2, 2 o,8, 1872. 



Spec. Char. C. Testa variabili crassd, subcordatd, postice angulatd, antice convexd, 

 extus laevigata aut irregidariter striata ; umbonibus elevatis ; deniibus later alibus incequalibus. 

 Length, fths of an inch; height, fths of an inch, but variable. 

 Localities. Bembridge {Morris), Osborne {Forbes). 



This is an abundant species in several parts of the Isle of Wight, and as it is variable 

 I have had two different forms represented. Its principal distinction or, I ought to say, 

 its claim to specific isolation, is a more prominent umbo, great tumidity, and an angu- 

 larity on the posterior side. Some old specimens have a thick shell in which the 

 impressions from the adductors are very deep. The large specimen figured by Mr. 

 Sowerby, Tab. 162, fig. 4, and said to be from New Cross, shows a more rounded 

 exterior than any I have from the Isle of Wight ; and if it be referable to this species 

 it must be a very aberrant form. Probably, however, it belongs to some other species 

 as the locality, " New Cross," would imply that it came from the Woolwich Beds (Lower 

 Eocene), whereas our Isle of Wight species belongs properly to the Upper Eocene. 

 Mr. Whitaker in his Memoir Geol. Surv., 1872, gives at p. 577 this species as from 

 Dulwich, with a mark of interrogation, but I have not been able to confirm it. 



Mr. Morris in his Catalogue gives it from Barton, but I have not seen it from that 

 marine locality. Mr. Sowerby has also given Barton as the locality for his figures 5, C. 



16. Cyrena obtusa, Forbes. Tab. B, fig. 13 a — c. 



Cyrena obtusa, Morris. Catal. Brit. Foss., 2nd edit., p. 200, 1854. 



— — Forbes. Mem. Geol. Surv., Isle of Wight, p. 149, pi, in, fig. 4, 1856. 



— — J. Lowry. Chart Brit. Tert. Foss., pi. ii, 1866. 



— (batissa) obtusa, Sandberger. Land- und Sussw.-Conch., p. 311, t. xx, 



fig. 3 a, b, 1872. 



