April, 1920] Marl Deposits in Ohio 175 



Gundlachia sp., one specimen, of an early stage, with the small 



anterior aperture and no Ancylus-like expansion; about 



2 mm. long and 1 mm. wide. 

 Physa gyrina Say, rather scarce. 

 Physa Integra Say, a few. 

 Physa heterostropha Say, scarce. 



Physa sayi Tappan, rather frequent, large, mostly broken. 

 Amnicola limosa Say, common, variable with respect to size 



and shape. 

 Amnicola lustrica Pilsbry, abundant, very variable as to size 



and shape. 

 Amnicola smaller and rather different; may be distinct 



(Dr. Walker). 

 Amnicola emarginata Kuster, scarce. 

 Lyogyrus granum Say, apparently; common. 

 Valvata tricarinata Say, common, most specimens of a some- 

 what peculiar form: umbilicus narrow, all three keels 



threadlike or even lamellar; some are scalaroid. 

 Valvata sincera Say, frequent, axial striae fine and slight; the 



largest has a diameter of 4.7 mm. 

 Pisidium compressum Prime, common, of different forms: the 



typical, and Iceiigattim (with the beaks unridged, of quiet 



water) . 

 Pisidium fallax Sterki, rather scarce. 

 Pisidium variabile Prime, common. 

 Pisidium pauperculum Sterki, abundant; different forms, 



especiall}^: crystalense, also recent in Ohio, and nyla?ideri, 



recent in Maine. A few specimens with partially reversed 



hinges. 

 Pisidium sargenti Sterki, rather scarce. 

 Pisidium adamsi affine Sterki, a few, like those from Meyer's 



Lake. 

 Pisidium abditum Haldeman, apparently, rather scarce. 

 Pisidium walkeri Sterki, scarce. 

 Pisidium scutellatum Sterki, scarce. 

 Pisidium ohioense Sterki, rather scarce, like recent specimens, 



e. g., from Garrettsville, Ohio. 

 Pisidium splendidulum Sterki, frequent. 

 Pisidium rotundatum Prime, scarce. 



Pisidium medianum Sterki, frequent, rather small form. 

 Sphaerium sulcatum Lamarck, frequent; one specimen with 



partially reversed hinge. 



