12 EOCENE MOLLUSCA. 
Cyclas 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. Cyrrna opovara, J. Sowerby. ‘Tab. B, fig. 3 a—d. 
Cycias oBovata, J. Sow. Min. Conch., t. 162, figs. 5, 6, 1817. 
Cyrrna — Morris. Catal. Brit. Foss., 2nd edit., p. 200, 1884. 
—  (corsicuLa) oBovata, Sandb. Land- und Sussw.-Conch., p. 261, t. xv, 
figs. 2, 2 a, 6, 1872. 
Spec. Char. C. Testé variabili crassd, subcordatd, postice angulatd, anticé convead, 
extus levigaté aut irregulariter striata ; umbonibus elevatis ; dentibus lateralibus inequalibus. 
Length, Zths of an inch; height, 3ths 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. Sury., 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, 6. 
16. Cyrena optusa, Forbes. Tab. B, fig. 13 a—e. 
Cyrmna oprusa, Morris. Catal. Brit. Foss., 2nd edit., p. 200, 1854. 
— Forbes. Mem. Geol. Surv., Isle of Wight, p. 149, pl. ili, fig. 4, 1856. 
— — J.Lowry. Chart Brit. Tert. Foss., pl. i, 1866. 
— (BATISSA) oBTUsA, Sandberger. Land- und Sussw.-Conch., p. 311, t. xx, 
fig. 3.a, b, 1872. 
