THE KANSAN ICE INVASION 



255 



is highly calcareous and carries a rich gastropod fauna/' 5 The species 

 enumerated bv Bever are noted below: 



Pyramidula shimekii 

 Sphyradium edentulum allicola 

 Pupilla muscorum 

 Bifidaria pentodon 

 Vertigo ovata 

 Euconulus fuhus 

 Polygyra midtilineata 



Pyramidula cronkhitei anthonyi 

 Vallonia gracilicosta (=costata) 

 Helicodiscus parallel us ( = linealus) 

 Surcinea lineala 



" a vara 

 Gallia humilis modicella 

 Planorbis antrosus (=bicarinatus) 



The Galba and Planorbis evidently represent the period when swamps pre- 

 vailed, with streams penetrating these areas. Such mollusks as Sphyradium 

 and Pyramidula shimeki represent a later time when the region was dry and 

 had become loess covered. 



In Louisa County, about a mile north of Columbus Junction, a fossiliferous 

 loess overlies the Kansan drift. In the lower part of the loess, which is here 

 twelve feet thick, the mollusks indicated below occur: 35 



Pyramidula strigosa iowensis 



( =Oreohelix iowensis) 

 pers pectiia 

 cronkhitei anthonyi 

 Polygyra multilineata 

 Zonitoides arborea 



" shimeki { — Pyramidula shimeki) 

 Euconulus fuhus 

 Vallonia gracilicosta 



Sphyradium edentulum allicola 

 Bifidaria pentodon 

 Helicina occulta 

 Succinea aiara 



" obliqua 



' grosienori 

 Galba humilis modicella 



The post-Kansan loess of Mills and Fremont Counties contains a rich fauna. 

 Good exposures have been studied at Hamburg, in Fremont County, and at 

 Kelly Creek and Oak Township, Mills County. Udden 37 lists the following 

 species: 



Helicina occulta 

 Leucochila Jallax 

 Bifidaria armijera 

 " pentodon 

 Zonitoides arborea 

 Pyramidula al'.ernata 



cronkhitei antlwnyi 



shimekii 

 Helicodiscus parallelus 

 Vertigo boVesiana 

 Succinea aiara 



Succinea obliqua 



' grosvenori 



" retusa 

 Vallonia gracilicosta 

 CocMicopa lubrica 

 Polygyra leai 



" midtilineata 



" hirsuta 

 Vitrea hammonis 

 Sphyradium edentulum allicola 

 Pyramidula cronkhitei anthonyi (eggs^ 



K Op. cit., p. 118. Modern names are used in this list. 

 ■ Udden, Geol. Iowa, XI, p. 113. 

 " Geol. Iowa, XII, pp. 167-175. 



