BIVALVES. 101 



ribs, some of them being peculiar extinct forms, whilst others 

 are either still living or are represented at the present day by 

 very similar species. Thus the common cockle (Cardium edule, 

 Linn.) of the Swiss Molassic seas occurs in the sandstones of 

 St. Gall, Lucerne, and Miinsingen; some Mediterranean species 

 (C. oblongum, Chemn., C. hians and C. tuberculatum, Linn.) are 

 met with in the Molasse of the Cantons of Berne and St. Gall. 

 The Indian cockle (C. indicum) has been found at the Belpberg, 

 and a Senegambian species (C. costatum, Linn. ?) near Berne. 

 The genus Cardium, which makes its first appearance in very 

 early times, was therefore abundantly developed in the Molassic 

 sea, where it included species the areas of distribution of which 

 are now widely separated. The fine genus Isocardia, in which 

 the heart-shaped valves are furnished with spirally twisted beaks, 

 is much less abundant. One species (/. cor, Linn.), which is 

 met with in the Mediterranean, and more rarely on the British 

 coasts, has been discovered near Rorschach. 



The Dimyaria with the impression of the sinuated mantle 

 (Sinupallealia) are represented by numerous families in the Swiss 

 Miocene sea. The Veneracea, the valves of which have large 

 beaks projecting over an internal concave lunula, furnish twenty- 

 seven species. No doubt they lived, like their existing repre- 

 sentatives, on shallow sandy shores, and buried themselves in the 

 soil. They are now distributed upon all coasts, but the greatest 

 number of species is found between the tropics. Several of these 

 tropical forms (such as Venus plicata, Gmel., V. multilamella, 

 Lam., and Dosinia Adansoni, Poli) formerly occurred in the 

 Swiss area; but with these were associated five more species 

 (Venus ovata, Mont., V. casina, Linn., V. verrucosa, Linn., Cy- 

 therea minima, Mont., and C. rudis, Poli) which now live in the 

 Mediterranean or on the European coasts generally. One spe- 

 cies (Dosinia lincta, Pult.), which has been found at the Belp- 

 berg, the Weinhalde, and the Rothsee, and near Niederhasli and 

 St. Gall, is still living on the coasts of England, in the Medi- 

 terranean, and near Senegambia; and another species (D. exo- 

 leta, Lam.), which may be obtained in the Molasse of the 

 Rothsee and at Imi in the Canton of Berne, has at present 

 the same distribution. 



The Psammobia furnish two large extinct species (Psammobia 



