TO GEOLOGY. 99 



of the columella, where it is disposed to put on an obscure 

 fold, is thicker. 



Eight species have been observed in England. One in 

 the Coral Rag, five in the London Clay, and two in the 

 Crag. M. Deshayes gives twenty-three in his Tertiary 

 Tables fourteen are from the Paris basin. 



In the Green Sand Formation of Jersey, Dr Morton 

 thinks he has observed casts of the Bulla. In the Tertiary 

 of Maryland, Mr Conrad has obtained one species, Bulla 

 acuminata (Sowerby). 





FAMILY MELANIANA. 



GENUS PASITHEA. (nobis.) 



Description. Shell turrited, sometimes umbilicate ; 

 mouth entire, angular above, somewhat effuse at base ; 

 columella smooth, thickened. 



Observations. The mouth of the shells in the genus pro- 

 posed above has a strong resemblance to the genus Mela- 

 nia.* It is, however, less effuse at the base, straighter and 



* The distinguished geologist, M. Brogniart, in his " Terrains du Vi- 

 centin," page 58, describes three species of Melania, two of which might 

 with propriety be placed in the genus Pasithea. He makes the following 



