been found in North America. No trace lias been discovered of any Ter- 

 tiary newer than the Miocene. 



All the Oligocene species were found by myself at Vicksburg, Missis- 

 sippi, a few of which are said by Prof. Hilgard to occur in the Jackson 

 Eocene. I found one only at Vicksburg, a solitary specimen of Fusimitra 

 conquisita, which is also a Jackson species ; and, I think, that any mixture 

 of Oligocene and Eocene forms was accidental after the latter fauna became 

 extinct. 



The Jackson group was so named by Prof. Eugene W. Hilgard in Ms 

 learned and able report on the Geology of Mississippi. 



