April, 1920] Marl Deposits in Ohio 183 



Gundlachia , one specimen; the same as from the Tinkers 



Creek marl, partly broken, but enough is left to show its 

 shape. 



Physa gyrina Say, common; different forms: typical, and 

 hildrethiana Lea. (Dr. Walker). 



Physa elliptica Lea, frequent. 



Physa Integra Say, rather scarce, with the whorls strongly 

 convex. 



Physa aplectoides Sterki, scarce. 



Aplexa hypnorum, Linnaeus, rather scarce, mostly young and 

 adolescent. 



Goniobasis livescens Menke, frequent; "a river form like the 

 one in the Sandusky River above Fremont." — (Mr. Calvin 

 Goodrich). This is a remarkable occurrence especially 

 since the snail was found over a wide stretch and at various 

 depths, so that it could hardly have been confined to a 

 stream, or streams, running through the marsh. 



Pomatiopsis lapidaria Say, frequent. 



Pisidium compressum Prime, scarce. 



Pisidium pauperculum Sterki, scarce. 



Pisidium abditum Haldeman, rather scarce, small and slight. 



Pisidium ohioense Sterki, a few. 



Pisidium rotundatum Prime, scarce. 



Pisidium medianum Sterki, a few, small. 

 Of Unionidae not a trace was found. 



In this fauna the "land-snails" are largely predominating, 

 composing about fifty species out of seventy-three gastropods, 

 and the proportion is still more marked with the numbers of 

 specimens. As previously mentioned, they were found over a 

 wide stretch, from bottom to top, and had evidently been living 

 there* and gradually buried. The region was evidently marshy, 

 possibly with streams running through it, with parts per- 

 manently above water covered with mosses and taller vegeta- 

 tion, inhabited by land snails favored by a moist atmosphere. 

 The water was probably generally shallow, its level changing 

 considerably with the seasons. This appears to account for 

 quite a number of things: the irregular and stunted growth of 

 many LymncBidcE and Planorbidce, the absence of Naiades and 

 Sphasria,t and the scarcity of Pisidia, also for the absence of 



*Except possibly part of those in the probable drift layer mentioned; unfor- 

 tunately an exact separate list of them has not been kept. 



jExcept G. occidentale Prime, which might have been expected. 



