THE LOESS OE NACHEZ, MISS. 307 



altemata and H. perspcctiva are now placed in the genus 

 Pyramidula, H concava in the genus Circinaria, and the re- 

 maining species of Helix in the genus Polygyrct, H fraterna 

 being a variety of P. monodon. The "Ackatina" is probably 

 Bulimulus, and not from the loess. At least it has not been 

 found in the loess along the Mississippi, though it is a char- 

 acteristic species of the southern modern terrestrial molluscan 

 fauna, and its occurrence as a fossil would not be surprising. 

 W. G. Binney frequently refers to the loess or "post-plio- 

 cene" fossils in his works on modern terrestrial molluscs, and 

 many of them are unquestionably from the bluffs of the lower 

 Mississippi, — some of them being specifically reported from 

 Natchez. In 1865* he reported two species of terrestrial mol- 

 luscs from the "post-pliocene of the Mississippi valley"(for the 

 most part undoubtedly loess), one of them being a southern 

 species which is known from the Natchez loess. In 1869! he 

 reported 19 terrestrial species from the same indefinite source. 

 Of these 15 species were found by the present author at Natchez. 

 They are the following: 



Hyalina (now Gastrodonta) ligera. 

 Macrocyclis (now Circinaria) concava. 

 Helix (now Pyramid 'it /a) altemata. 

 Helix (now Pyramidula) perspectiva. 

 SI rob i la (now Strobilops) labyrinlhica. 

 Helix (now Polygyra) stenotrema. 

 " " " hirsuta. 



" " " monodon. 



pall lata. 

 " " inflecta. 



" " " albolabris. 



" " " elevata. 



" " " exoleta. 



" " " profunda. 



Succinea obliqua (now oralis Say). 



Of the remaining four species one, Helix (now Pyramidula) 

 solitaria does not belong to the southern fauna. % 



* Smith. Miscell. Coll., no. 144, Sept., 1865. 



tin Binney and Bland, — Land and F. W. Shells of N. Am. — Smith. 

 Miscell. Coll., p. 104; Feb., 1869. 



tThe writer has reason to believe, from private correspondence with 

 Mr. Binney, that the shells reported under this name are Pyramidula 

 slrigosa ioensis, a species belonging to the northern loess. 



