502 MICHIGAN SURVEY, 1905. 



considered the typical form {ovalis Gld.), is that represented by Fig. 

 109, copied from Binney, and is characterized by its very short, rather blunt 

 spire, elongated bod}^ Avhorl, and patulous aperture, expanding anteriorly. 



Pilsbry's var. magister is distinguished by its large size, less developed 

 spire and larger aperture. It 'has been cited from Michigan by Pilsbry,. 

 but I have never seen any specimens from this state that answer the descrip- 

 tion. The figure is from the type in the collection of the Philadelphia 

 Academy. Tryon's var. decampii is well marked typically by its elongated^ 

 compressed form, peculiar color and black-edged lip. But the color and 

 form are not always correlated. Specimens similar to peoriensis in form^ 

 and to decampii in color are not uncommon. In form this variety, typically,. 

 is similar to a well marked race of larger size, which is quite characteristic 

 of the northern part of the state, and which has been erroneously quoted as 

 S. higginsi Bid. In the western part of the state a much larger form is 

 found, with a somewhat more elongated spire than in the typical form, which 

 seems to be nearer Lea's retusa (fig. 107). Calkins' S. calumetensis , (fig.. 

 108), is a doubtful form scarcely, if at all, different from the ovalis of Gould. 



A very large form from East Saginaw;, collected by the late Dr. G. A. 

 Lathrop, seems to bear the same relation to the elongated northern form 

 referred to in connection with var. decampii that typical retusa apparently 

 does to the ovalis of Gould. The elucidation of the inter-relationship of 

 these puzzling forms requires careful anatomical comparison and is one of 

 the most important problems in regard to our terrestrial mollusca, which still 

 remains to be solved. 



SUCCiNEA OVALIS Say. 



Shell ovate, pale green, yellowish-green, amber-colored or cin- 

 I ; \ j^^ ereous, thin and fragile, pellucid; shining, minutely wrinkled or 

 - </^!jV, striated; whorls 3, the last very large and much expanded, and 

 ^y/ijii more or less oblique; spire very small, not prominent nor pointed; 

 ^//J suture distinct, impressed; aperture oval, large and expanded. 

 i^ columella thin, sharp, narrowed; peristome thin. 

 Fi^Tus. ^1^- 18 to 25 mm. 



*S. ovalis. 

 (Binney.) 



Succinea ovalis, Say, Jour. A. N. S. P., I., 15, (1817). 



obliqua, W. G. Binnev, Man'. Am. Land Shells, 341, fig. 371, 



(1885). 



— campestris, Sager, Doc. H. Rep. Mich., 1839, 420, separate, p. 14. 



\ Miles, Rep. Geol. Surv. Mich., 236, (1861). 



■ ohliqua. Miles, Rep. Geol. Surv. Mich., 236, (1861). 



— , Currier, Shell-bearing Moll. Mich., 4, (1868). 



^ , DeCamp, Shell-bearing Moll. Mich., 5, (1881). 



, Walker, Rev. Moll. Fauna Mich., 17, (1894). 



Although not as abundant as either retusa or avara, this species has a gen- 

 eral distribution in the lower peninsula. It has not yet been reported from, 

 the upper peninsula except on Isle Royale. Occasional specimens are very 

 close to the eastern form known as *S^. totteniana Lea, both in color and form. 



The accepted nomenclature of this species {S. obliqua, Say), has been er- 

 roneous for many years. Say's original description of S. ovalis in 1817 has 

 priority over his later use of obliqua for another form of the same species. 

 Dr. Amos Binney attempted to apply ovalis to the species now known as. 



