POSTGLACIAL BIOTA OF THE GREAT LAKES REGION 137 



Pisidium compresswn Ancylus parallelus 



variabile Planorbis deflectus 

 adamsi qffine " campanidatus 



medianum Galba galbana 

 splendididum " humilis rustica 



scutellatum 



Several deposits in Bay County (of doubtful age) are described by Cooper. 68 

 On the east line of section 23, Hampton Township, extending south from Nebo- 

 bish Avenue almost to the section corner, the annexed section occurs. 



Sand and gravel 10-20 inches 



Bed of muck 

 Clay 



Shells are found in all three strata. Cooper believes that the region was a 

 swamp during Nipissing or late Algonquin time; 15 species of mollusks 

 occur. 



Elliptio gibbosus? Goniobasis livescens 



Sphaerium flavum Physa gyrina hildrethiana 



" simile(= sulcatum) Planorbis antrosus 



Pisidium adamsi qffine " trivohis 



compressum Galba catascopium 



" variabile " obrussa decampi 



" virginicum Succinea retusa 



" trapezoideum 



A second locality is on the north line of section 10, Merritt Township, not 

 far east of the northwest corner. In a drain there was four and a half feet of 

 white sand at the top, which was underlaid by a thin layer of muck above the 

 clay. The section was not unlike that at the preceding locality. The deposit 

 of muck is thot to represent late Algonquin or possibly Nipissing time, while 

 the sand is believed to represent Nipissing time. Life is poorly represented 

 here, Goniobasis livescens being the only animal seen. 



4. Nipissing Great Lakes 



The three deposits described below are believed to have been laid down dur- 

 ing the Nipissing stage: 59 



(1) In a drain about three feet deep on the west line of the northwest quar- 

 ter of section 7, T. 13 N, R. 5 E, mollusks were found in a silt-clay, either of 

 lake origin or deposited more recently by the river. The elevation is about 

 587 feet above tide. The assemblage of species suggests that the locality 

 was a lake shore upon which the shells were cast by the waves. 



H Op. oil., p. 252. 

 *' Cooper, op. cit. 



