314 Viscount d'ARCHiAC and M. de Verneuil 



The shells of the TuhicoloB appear to be completely wanting in the Palgeozoic 

 formations. The Pholadariee, the Solenacece, the Myarice, the Mactracea, and the Cor- 

 bulacecB, are very seldom represented. Among the NymphacecB the Sanguinolaria are 

 the most plentiful, particularly in the Devonian system, in which there are sixteen 

 species, found in the limestones of the Eifel and of Elbersreuth. Two of these are 

 found in the lower system, and the grauwacke of the Rhenish provinces contains 

 five. Ten are Carboniferous, the greater part from England, and some of these 

 reappear at Peretki in the Valdai and in the government of Kaluga. The San- 

 guinolaria angustata, Phil., and S. sulcata, Miinst., are common to the whole series. 

 Of seven Lucince five are Devonian and from the Eifel, and the remaining genera 

 of this family are unimportant. A single Cyclas is mentioned in the freshwater 

 limestone, subordinate to the coal-beds of Westbury in Staffordshire. (Silur. Syst., 

 p. 84.) The Veneres are Carboniferous, and the Pullastrce Devonian ; they are only 

 mentioned as found in England and Belgium. 



The family of Cardiacea increased greatly during the long accumulation of Pa- 

 laeozoic sediments. The numerous forms of the shells of this family were then ex- 

 tremely varied, as they were during the secondary and tertiary periods, and as they 

 are in the present seas. We shall see as we proceed, that in general those genera 

 which have been capable of resisting all the revolutions of the globe, and which 

 from the commencement showed this tendency to an almost infinite variety of form, 

 but have preserved certain characters which bring them near to the primitive type, 

 have not ceased to exhibit the same polymorphism even to the present time. 



Several divisions have recently been established in the genus Cardium of the older 

 beds, which we adopt as subgenera. The Cardiomorphfs* are Carboniferous and from 

 Belgium ; the Lunulacardi(E-f are Devonian, from Elbersreuth and the Fichtelge- 

 birge ; the Cardiol^X, one only excepted, are also Devonian, and from the Clymenia 

 limestone of Elbersreuth ; the Pleurorhynchi^ or Conocardia\\ (a subdivision in which 

 we only leave the new species^) are of little importance. The genus Cardium, as 

 we now keep it, still includes fifty-three species : the Silurian beds contain five which 

 are of shght interest, but one of which passes into the Devonian system ; forty-four 

 are from the Clymenia and Orthoceratite limestone of Elbersreuth and the corre- 

 sponding beds of the banks of the Rhine. The C. palmatum, Goldf., is the most 

 common of these species in Westphaha, the Duchy of Nassau, the country of Wal- 

 deck, the Fichtelgebirge, and it is also found in Nova Zembla**. In the upper 



* De Koninck, Recherches Anim. Foss. Belgique, p. 101, 1842. — (Note, April IS-tS.) 

 t Count Miinster, Beitrage, Heft iii. p. 69, 1840. J Broderip, Silur. Syst., p. 617, 1839. 



§ Phillips, Geol. Yorkshire, part 2. p. 210, 1836. || Agassiz. 



f We have provisionally left in several new genera, such species as were not known before under 

 another name. 



** A specimen from that country is in the Museum of Paris. 



