IOWA ACADEMY OF SCIENCES. 



Ill 



Iowa, than exists to-day between the surface conditions of the 

 same regions. This fact is irrefutable, and must not be over- 

 looked in any discussion of the conditions under which loess 

 was deposited. 



TABLE OF SPECIES.* 



*The nomenclature of Pilsbry and Johnson's recent Catalogue' of the Land Shells of 

 N. Am is here employed. As there are some departures fpotn former usage, the 

 changes are here noted: 



Species 2, 3 and 4 were formerly included uader V. puj/ihella. 



Species 5 and 6 were referred to the genus Memdon, and 7 and 8 to Stenotrema. 



Species 9 was included under Stro/ufi labyrinthica. 



The species of Leachochila and Bifidaria were included in Pupa. 



Species 18 was called Ferussacia subcylindrica. 



Vitrei, Conulus and Zonitoides were formerly placed in the genus Zmita, and No. 19 

 was called Zonitoides radiatulus. 



Pyramidula was formerly Patula. 



Succinea grosvenorii was called S. lineata. 



+Oae specimen of P.profun'ix was found by the writer in exposure C (since con- 

 siderably altered) in 1890. 



'i^Three specimens of this species were collected in exposure in 1890. 



IIThe writer formerly regarded this as a form of Zon. nitidus. Mr. Pilsbry, however, 

 regards it as distinct, and in deference to his oplnioQ his name is retained. 



TThe form of S. obliqua which occurs most commonly in the loess is the narrower, 

 smaller form with more extended spire, such as is not uacommon (living) in Iowa and 

 as far east as Indiana. As itis difficult to distinguish between some forms of this and 

 &'. grjsvenorii, the two species are not here separated, as more time for careful compari- 

 son of the large sets will be required. 



