30O NATURAL HISTORY BULLETIN. 



While it was at first regarded as distinct from the loess of 

 the upper Mississippi drainage, it is indistinguishable from 

 it in its physical characters, — especially from that which may 

 be designated as Missouri river loess. There are certain pecu- 

 liarities of the fossil fauna of the southern deposit which have 

 already received some notice, but for the most part the refer- 

 ences to them are vague and unsatisfactory and do not suffi- 

 ciently set forth their significance. 



It was the writer's good fortune to visit Natchez (and also 

 Vicksburg) in May and June, 1898. The visit was made 

 chiefly for the purpose of studying the fossils of the loess and 

 comparing them with the modern molluscan fauna now in- 

 habiting the same region. As a result of this investigation 

 more than 4,600 fossil shells were secured; and some additions 

 were made to the collections of modern molluscs from Missis- 

 sippi and adjacent states made by the writer in previous years. 

 The season, however, was very unfavorable for collecting liv- 

 ing snails because of the long-protracted drought which caused 

 them to hide away. This probably accounts for the compar- 

 atively small number (less than 900 specimens) of modern 

 snails in the Natchez collection, of which more than one-half 

 belong to a species (Succinea grosvenorii} not represented in 

 the local loess. 



In all more than fifty exposures of loess were studied at Nat- 

 chez, and several were examined at Vicksburg, where but one 

 day was spent. The location of the principal exposures which 

 received attention at Natchez is shown in the accompanying 

 map. The topography of the region is striking. The Mis- 

 sissippi has cut away the deposits on the east side until bluffs 

 exceeding 200 feet in height face the river. In addition to this 

 smaller streams have washed out deep gullies, whose almost 

 perpendicular sides rise from 50 to nearly 200 feet. In all the 

 region which was investigated the highest points are uni- 

 formly close to the river, while the outlying region is much 

 lower. This is well illustrated by the ridge on which Natchez 

 stands. Reference to the map will show that the altitudes* in 



""These were obtained in part from barometric readings, and in part 

 from more exact data furnished by Captain Babbit of Natchez. 



