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Genus Osteodesma, Dosuayes. 



0. corruscans, Scaccbi.; syn. Lyonsia striata, Mont.; Mya 

 nitida, Fab.; Pandorina corruscans, Pliil., vol. i. Only 

 a single valve has been found. 



Gcnus Thracia, Leach. 



Thracia fossilc.s. 

 A fossil specics of Thraeia ?, in tlie form of casts, is found 

 in Bed ISIo. 2, the yellow saud. (E. Forbes). 



Genus Galeomma, Tartonii ? 



G. turtonii, Sowb. Rathor common attaclied by a silk 

 byssus to sunken rocks. 



VII. Familia LITHOPHAGA, Lamk. 



Geniis Saxicava, Lamk. 

 S. arctica, PLil. Rather rare. In caves. 



Gcnus Petricola, Lamk. 



P. lithophaga, (Venus) Retz. Abundant in tho calcareous 

 sandstoue rocks. 



Gcnus Venerupis, Lamk. 



V. irus. L. Common. 

 V. decussata, Phil. Rare. 



VIII. Familia KYMPHACEA, Lamk. 

 Genus Psammobia, Lamk. 

 P. vespertina, L. Common. 



