I 



PTEROPODA. 323 



CuviERA, with a cylindrical shell, 

 Psyche, Avith a globular shell, and 

 EuRYBiA, with a hemispherical shell(l). 



Pyrgo. 



It is thought that we may approximate to the Hyaleae, this very 

 small fossil shell discovered by M. Defrance. It is very thin, glo- 

 bular, and divided by a very narrow transverse cleft, except before, 

 where it becomes somewhat widened. 



(1) See the Mem., of M. Rang, Ann. des Sc. Nat., Novemb., 1827, and March 

 1828. 



N.B. Several Pteropoda have been discovered in a fossil state. M. Rang has 

 found, near 15ourdeaux, Hyalese, Cuvieriac, and Cleodorse. See Ann. des Sc. Nat. 

 August 1826. The Vaginella of Daudin is a Cresis according to M. Rang; it has, 

 in fact, all the characters of the latter. 



