116 



MOLLUSC A. 



ORDER PULMONATA. 



No. 304. Helix Turonensis, Desh. 



Of tliLs inoperculate pulmoniferous genus, 3400 

 species are living. They are fossil since the Cre- 

 taceous. Family Helicidfe. Miocene Tertiary, 

 Grund, Hanover. 



No. 305. Helix Tryonii, New. 

 Tertiary, Santa Barbara Is., California. 



Nq. 306. G-asteropod, enlarged by silica. 



The curious phenomena of tiie enlargement of shells, crinoid joints, &c. , 

 by a separation of the parts by intruded silica, requires further explanation. 

 This example is from the Carboniferous of Barren Co.,'*Ky. 



