162 FULLER AND CLAPP MARL-LOESS OF LOWER WABASH VALLEY 



liocality 3, east of New Harmon}" : 



Conulus fulvus, Drap. 

 Bifidaria armifera, Say. 

 Vertigo tridentata, Wolf. 



Locality 4, south of New Harmony : 



Zoniloides arboreus, Say. 

 Conidus fulvus, Drap. 

 StrobUops labyrinthica, Say, 

 Folygyra hlrsuta, Say. 



Locality 5, southeast of Kilroy : 



Selenites concava, Say. 

 Folygyra thyroides, Say. 



Locality 6, southwest of Stewarts ville 



Zoniloides arboreus, Say. 

 Helicodiscus Uneatus, Say. 

 Conulus fulvus, Drap. 

 StrobUops labynnthica. Say. 



Locality 7, west of Mounts : 



Lininea humilis, Ssiv. 

 Planorbis parvus, Say. 

 Planorbis bicarinatus. Say. 



Vallonia cyclophorella, Ancey. 

 Succinea lineata, TV. G. B. 

 Pomatiopsis lapidaria. Say. 



Polygyra monodon, Kack. 

 Succinea lineata, W. G. B. 

 Helicina occulta, Say. 

 Pomatiopsis lapidaria, Say. 



Succinea lineata, TV. G. B. 

 Polygyra elevata. Say. 



Polygyra hirsuta, Say. 

 Polygyra thyroides. Say. 

 Succinea lineata, TV. G. B. 

 Limnea humilis, Say. 



Valvata tricarinata, Say. 

 Pisidium variabile. Prime. 

 Pisidium compressum. Prime. 



TVith the exception of a single specimen of Limnea humilis. Say, which 

 was found at the Stewartsville exposure, aquatic or semi-aquatic species 

 were found only at the exposure near Mounts. At this point, notwith- 

 standing there were no observable variations from the type of silt pre- 

 vailing at the other exposures, all of the species found were aquatic. 

 This difference of the fossil fauna is probably an indication of marked 

 differences in the physical conditions attending the deposition of the 

 silts, the character and significance of which will be discussed on a sub- 

 sequent page. 



Terraces. — Not only do the marl and common loess show marked dif- 

 ferences in the composition and structure, but they also exhibit a strik- 

 ing difference in topographic expression. The common loess, as has 

 been stated, occurs in any given locality as a mantle of a moderate and 

 rather uniform thickness, conforming with the inequalities of surface. 

 The marl-loess, on the other hand, occurs in deposits of relatively great 

 thickness, burying all the minor irregularities of the till or rock surfaces 

 and presenting numerous instances of extensive flats or broad, gently 

 sloping terraces. 



