POST-WOODFORDIAN MOLLUSKS 21 



Helioodisous parallelus (Say) 1821 



Planorbis arellelus Say 1821, Acad. Nat. Sci. Philadelphia Jour., v. 2, 

 p. 164 (corrected to parallelus in the index , p. 407). 



Helioodisous parallelus (Say), Pilsbry 1948, Land Moll. N. America, 

 v. 2, pt. 2, p. 62 5, fig. 339. 



This small discoid shell is represented in the present collections by a 

 single specimen found at the 8- to 10-foot level at locality 135-1. Although it 

 has been described as a bog species by Ingram (1946, Nautilus, v. 59, p. 91), 

 one example here among many thousands of shells does not indicate that it 

 flourished among the molluscan assemblages under observation. 



Family Succineidae 



Genus Suooinea Draparnaud 1801 



The succineids are an ancient group of terrestrial gastropods with simple 

 shells featuring a large ultimate whorl and aperture and scarcely four whorls. 

 On the basis of the soft anatomy, four genera are recognized, but in general 

 the shells do not reflect this. Therefore, fossil shells are referred to modern 

 genera with varying degrees of confidence, including none at all. This report 

 uses Suooinea as the generic name, with the reference to other genera enclosed 

 in parenthesis as if they were subgenera. Considering the difficulties involved, 

 it would seem better, for paleontologists at least, if the modern genera were 

 considered subgenera of the genus Suooinea. 



The succineids are worldwide in distribution, and are found on all 

 continents as well as on many oceanic islands. 



Suooinea (Oxyloma) retusa Lea 1834 



Suooinea retusa Lea 1834, Amer. Philos. Soc. Trans., v. 5, pi. 19, 

 fig. 86. 



Oxyloma retusa (Lea), Pilsbry 1948, Land Moll. N. America, v. 2, 

 pt. 2, p. 785, pi. 2, figs. 25, 26. 



Suooinea retusa was recovered from three faunal associations at Strawn 

 NE locality 135-1, and in these the species was represented by only a few 

 shells. These were unusually small, but they bore other characters of the 

 species, especially the shape of the shell, which is quite distinctive. Living 

 colonies of S. retusa inhabit the wet, brushy borders of the lake, especially 

 southwest of boring 135-1, but these modern examples have shells unusually 

 large for the species. The significance of these observations is not clear. 

 S. retusa is found principally in northern United States and southern Canada, 

 invariably in wet situations near streams, ponds, and lakes. 



Suborder Orthurethra 

 Family Pupillidae 



Genus Vertigo Milller 1774 



The tiny shells of the pupillids are typically elongate spiral in form, 

 rimate, ovoid, with flaring peristome around an aperture that usually contains 

 a series of one to six or more denticles, although sometimes bearing none. The 

 family is divided into several genera, all differentiated primarily on the basis 

 of shell characters. The genus Vertigo is one of the most modified of the genera 

 The family is not only worldwide in its present distribution, but it is one of the 



