HANNA AND JOHNSON: MOLLUSKS OF KANSAS. 113 



LIST OF RECENT SPECIES. 



Sphxriimi sp? Vallonia gradlicostata Reinhardt. 



Lampsilis parva Lea. Vallonia parvula? Sterki. 



Qimdrula lacliry)iiosa Barnes. Pupoldes marginatus Say. 



Anodonta sp? Bifidaria procera cristata P. & V. 



Physa anatina Lea. Bifidaria armifera Say. 



Planorbis bicarinatus Say. Bifidaria holzingeri? Sterki. 



Zonitoides miniscula Binney. Bifidaria tappaniana C. B. Adams. 



Zonitoides singleyaua Pilsbry. Sucdnea grosvenori Lea. 



MIOCENE OF THE REGION. 



On Prairie Dog creek, between Norton and Long Island, 

 there are many fine exposures of what is generally known as 

 Loop Fork. According to Matthew* this belongs in the upper 

 Miocene series, and the short-legged rhinoceroses are the most 

 abundant fossils. 



The upper layer of this formation is the most conspicuous, 

 as a hard layer of porous white limestone caps most of the 

 hills along the route. This layer weathers poorly, and in the 

 majority of places exposes a perpendicular section on the 

 hillside. Beneath this there are many layers of sand and other 

 rocks, which are well exposed in a deep ravine south of Long 

 Island about five miles. At Almena a beautiful yellow sand is 

 exposed in great quantities. The layer is about forty feet 

 thick, and two mastodon skeletons are exposed. 



All of the strata are fossil-bearing, rhinoceroses being found 

 most abundantly, but many other groups are common. Eu- 

 phorbia seeds were found in all the layers examined. 



The formation is doubtless of Miocene lake origin, and may 

 contain fossil land shells in some places, but none were found 

 by us. These are occasionally found in the John Day region 

 in Oregon and the White river Miocene of Colorado, from 

 which it may be inferred that they exist sparingly in the 

 Loop Fork. Those land shells found in the former two di- 

 visions of the Miocene belong to a warmth-loving fauna, and 

 as they are not greatly different in general character from 

 species inhabiting the Carolinian zone at the present time, it 

 may be supposed that the climate of the Miocene period was 

 not essentially different from that of the region at the present 

 time. 



In later times there has been a gradual increase in cold, 



• W. D. U»tth»iv, Bull. Am. Mui. K«t. Hi.t. Ill, p. 65. 



