314 NATURAL HISTORY BULLETIN. 



ern loess, such as Helicina occulta, Succinea grosvenorii, Py ra- 

 ni idula striatella, Val Ionia gracilicosta, Polygyra multilineata 

 and Pupa muscorum, are wholly absent from the southern 

 loess, as, with the exception of 61 grosvenorii, they are from 

 the modern fauna of that region, while Succinea avara, so 

 common in the north, and so frequent there as a fossil, is very 

 rare in both the fossil and modern faunas of Natchez. 



More than one-half the species in the Natchez list of fossils 

 have also been found in the northern loess, while the follow- 

 ing eighteen species are thus far known only from the loess of 

 the south: 



Helicina orbiculata Omphalina kopnodes 



Polygyra fraudulenta Viirea placenlula 



' ' inflecta Gastrodonta ligera 



" albolabris " multidentata' 



" exoleta Pyramid ula altemata costata 



" palliata Punctum pygmirum 



" obstricta btrobilops labyranthicaf probably*) 



' ' elevata 



" thyroides bucculenta 



1 ' stenotrema 



Polygyra albolabris and Punctum pygnueum are the only 

 species in this list which, judging from present distribution, 

 are likely to be found in the northern loess. The remaining 

 twenty-four of the species listed in the table of fossils have all 

 been found more or less abundantly in northern loess. 



Several additional points of interest are presented by some 

 of the Natchez fossils. Only two of the shells of Polygyra 

 thyroides bucculenta have the parietal tooth. The remaining 

 edentate specimens somewhat simulate P. clausa, but they 

 are less elevated, and not so heavy nor so coarsely striate as 

 the shells of that species. The parietal tooth is easily broken 

 off in the fossils of this and other species, and in identifying 

 fossil species, too much importance must not be attached to 

 its absence. 



The fossil Polygyra hirsuta is the small form, approaching 



*The 5". labyrinthica of the earlier reports on northern loess fossils is 

 probably all .S". virgo. 



