POST-WOODFORDIAN MOLLUSKS 15 



Fossaria parva (Lea), F. C. Baker 1928, Freshwater Moll. Wisconsin, 

 pt. 1, p. 285, pi. 18, figs. 1-5. 



Lymnaea parva is a small gastropod, the shell varying from 4.5 to 9 mm 

 in length. The shell is slender, and the whorls are rounded. Like L. dalli 

 it is more often found out of the water than in it; Baker (1928, p. 287) notes that 

 L. parva "is more prone to leave the water than any other member of the family." 

 This small gastropod occurs throughout the two bogs studied and is found in 11 

 of the 27 faunal assemblages; it is slightly more numerous in the assemblages 

 recovered at the Batavia site (locality 136) . Although it does not occur at any 

 level in abundance, its distribution throughout the various sampled levels indi- 

 cates that it was probably a part of the indigenous molluscan fauna. 



Genus Pseudosuooinea F. C. Baker 1908 



Baker removed the species Lymnaea columella of Say 1817 from the genus 

 Lymnaea and established the genus Pseudosuooinea on the basis of the peculiar 

 succineiform shape of the shell and certain anatomical characteristics. This 

 change has not met with universal approval, but most authors have followed 

 Baker. 



Pseudosuooinea oolumella (Say) 1817 



Lymnaea oolumella Say 1817, Acad. Nat. Sci. Philadelphia Jour., v. 1, 

 p. 14. 



Pseudosuooinea oolumella (Say), F. C. Baker 1928, Freshwater Moll. 

 Wisconsin, pt. 1, p. 272, pi. 10, figs. 9-12, 20. 



The shell of P. oolumella, as the name suggests, greatly resembles the 

 shells of Suooinea , except that it has more whorls than the members of the 

 latter genus. Adults are as long as 12 mm, but the single shell recovered in this 

 study, from the 10- to 12-foot level of locality 135-1, is much smaller although 

 it has nearly five whorls. The environment at the bog lake seems appropriate, 

 but the single shell recovered indicates that P. oolumella was not a significant 

 element of the molluscan fauna. P. oolumella is widely distributed in North 

 America. The genus Pseudosuooinea extends through Central and South America. 



Family Planorbidae 



Genus Gyraulus Agassiz 1837 



The genus Gyraulus is composed of small planorbid gastropods which 

 live as aquatic pulmonates, principally on vegetation, in ponds, lakes, or the 

 quiet parts of streams. They are inconspicuous because of their small size and 

 dark color, but may often exist in abundant populations. Species of Gyraulus 

 are persistent and often conspicuous elements in fossil molluscan assemblages 

 from water-laid sediments. The genus is worldwide in distribution. La Rocque 

 (1968, p. 483) points out means of distinguishing members of the genus Gyraulus 

 from others with which they might be confused. 



Gyraulus altissimus (F. C. Baker) 1919 



Planorbis altissimus F. C. Baker 1919, Nautilus, v. 32, p. 95, pi. 7, 

 figs. 7-10. 



Gyraulus altissimus (F. C. Baker), F. C. Baker 1928, Freshwater Moll. 

 Wisconsin, pt. 1, p. 382, pi. 22, figs. 10-17. 



