POST-WOODFORDIAN MOLLUSKS / 



as discussed below, there is evidence that some shells reached the deposit 

 from outside the lakes. 



The original basins in which the two bogs developed are judged to be as 

 old as 10,000 to 12,000 years, inasmuch as the lowermost finite date of about 

 9,000 radiocarbon years B.P. (Coleman, 1974) is approximately 5 feet above 

 the base of the bog sediments. A reasonable extrapolation based on the rate of 

 dated sedimentation produces this approximation. 



SYSTEMATIC ACCOUNT OF MOLLUSCAN SPECIES 



The molluscan fauna is listed here in systematic order, and reference is 

 made to the original description of each taxon, to a standard work using the 

 present name combination, and to a description and illustration of each kind 

 of shell. 



Class Pelecypoda 



Order Prionodesmacea 

 Family Unionidae 



Fragments recognizable as those of unionid mussel shells were recovered 

 from time to time in auger samples from each of the three holes augered, but 

 none of these was large enough to do more than relate them to the pelecypod 

 family. No hinge teeth were recovered. 



Order Teleodesmacea 

 Family Sphaeriidae 



Genus Sphaeriwn Scopoli 1777 



H. B. Herrington, in his revision of the North American Sphaeriidae 

 (1962), recognized 35 kinds of these animals, 31 of them native to North 

 America and 4 kinds judged to have been introduced from Europe. The sphae- 

 riids were distributed by Herrington among 3 genera — Sphaeriwn , having 12 

 recognized species; Pisidiwn , having 22 species; and the New World genus 

 Eupera , which is represented in North America by the single species oubensis . 

 Burch(1972), in his illustrated key to the Sphaeriidae of North America, added 

 4 species of Pisidiwn to the list recognized by Herrington. 



Sphaeriwn seouris (Prime) 18-51 



Cyclas seouris Prime 1851, Boston Soc. Nat. Hist. Proc, v. 4, p. 160 

 Sphaeriwn seouris Prime 1865, Monogr. Amer. Corbiculidae, p. 49. 

 Sphaeriwn seouris (Prime), Herrington 1962, Revision Sphaeriidae 

 North America, p. 26, pi. 1, fig. 2. 



The shell of S. seouris is small for the genus, usually not more than 

 8 mm in length; the beak is usually, but not invariably, calyculate. The species 

 occurs in seven of the faunal assemblages; it is distributed through various 

 levels and at each of the three localities (fig. 3) . In no assemblage were the 

 shells numerous; in fact they should be categorized as rare since numbers of 

 valves ranged from 1 to 7 in any particular assemblage. 



