POSTGLACIAL BIOTA OF THE GREAT LAKES REGION 143 



Vilrea hammonis{—radiahda) Pyramidala solitaria 

 " indentata " alternata 



Circinaria concaiia " cronkhitei anthonyi 



Polygyra profunda Bifidaria contractu 



" multilineata Succinea avara 

 " albolabris " retusa, var. 



" zalela Physa species (broken) 



" clausa Pomatiopsis lapidaria 



mitcheliana Pisidium compressum 



thyroides Pisidium fallax 



" elevata Unio, fragments 



From Holmes County, Claypole 70 has recorded the presence of a fauna which 

 is probably post-Wisconsin. The locality is near Millersburg, which is near 

 the edge of the Wisconsin drift. The deposit was found in a ditch in a swamp. 

 Six feet of peat covered a bed of shell marl, in or on which a Megalonyx skeleton 

 was lying. The animal died, it is evident, after the marl had been formed. 

 The upper layers of the marl contain the following species of mollusks: 



V alvata tricarinata Planorbis parvus 



Atnnicola limosa Sphaerium simile 



" limosa porata Pisidium virginicum 



By far the most complete postglacial fauna yet described from marl deposits 

 is listed by Sterki from two localities in northern Ohio. "One locality is in 

 Erie County, a few miles east of Sandusky Bay and a few miles west of Castalia, 

 and appears to be of comparatively recent date, the marl beds possibly still 

 forming at some places. The other locality is in the northeast corner of Sum- 

 mit County, where it was exposed by the dredging of Tinker's Creek. It 

 appears to be covered, at least in part, by several feet of sand and gravel. It 

 is very rich in fossils but its fauna is radicllay different from that of the Cas- 

 talia locality. " It has not been possible to correlate these deposits with any 

 of the stages of the Glacial lakes. 



In the Castalia beds there are 75 species and races, 50 of which are land 

 species and 25 are fluviatile species, or 66 per cent land species. In the Tinker's 

 Creek fauna there are but 8 land species and upwards of 45 fluviatile species, 

 or only 15 per cent land species. Of the fluviatile species, only 10 are common 

 to both localities and but one, Planorbis parvus, is abundant in both. The 

 presence of Acella haldemani and Lymnaea stagnalis appressa in the deposit 

 at Tinker's Creek is especially noteworthy, both being rare in Ohio. The lists 

 of species from these localities with notes, prepared by Dr. Sterki, are given 

 below: 



Fossil mollusks from Castalia marls Zonitoides minuscula, common to abundant. 



Erie County Vitrea hammonis, common. 



Gastrodonta ligera, rather scarce. Vilrea wheatleyi, a few. 



Zonitoides arborea, frequent. Vilrea rhoadsi, one not full grown. 



'"> Amer. Geol., VII, pp. 122-132, 149-153. 



