MOLLUSCA OF MICHIGAN— WALKER. 



501 



^uccinea ovalis. 



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

 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). 



Tig. 110. S. retusa migister. Fig. 111. S.retusoi decampii. X2. Fig. 112. S. retusj peoriensis. x2 

 Var. MAQISTER Pilsbry. 



"Distinguished from S. retusa Lea, by its larger size, less developed 

 :spire and larger aperture.^' 



Alt. 18, greater diam. 9^-10, length of aperture 13-14 mm. 

 .Succinea retusa magister, Pilsbry, Naut. XIL, 103, (1899). 



[Var. DECAMPII Tryon. 



Ovate-conic, translucent, finely striate, polished; spire short, acute; 

 :suture moderately impressed; whorls 3, very oblique, narrow, flattened; 

 aperture narrow, ovate; columella slightly incurved; yellowish-ash color, 

 edge of aperture black. 



Alt. 10, diam. 5 mm. 

 .Succinea decampii, Tryon, Am. Jour. Con., XL, 237, pi. II., fig. 23, 



(1866). 



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



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



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



Var. PEORIENSIS Wolf. 



Ovate, spire obtuse, more elevated than in the typical form; body- 

 ivhorl less elongated and more inflated; aperture nearly oval, somewhat 

 .angular above and regularly rounded below, scarcely patulous. 



Alt. 10, diam. 6 mm. 

 .Succinea peoriensis (Wolf), Walker, Naut. VII., 127, (1894). 



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



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



This species usually known as S. ovalis, Gould non Say, is one of the 

 :most abundant and variable species found in the state. The variation is 

 :so great and the characteristics afforded by the shells alone are so slight 

 and elusive, that until the anatomical details have been worked out, which, 

 perhaps, may afford more reliable speciflc features, it is questionable whether 

 .any satisfactory arrangement can be made. There are several well marked 

 varieties found in Michigan, which might be satisfactorily described from 

 :selected examples, but, in any considerable number of specimens, they seem 

 to intergrade almost without limit. Under these circumstances it does not 

 :seem wise to attempt to do more than to define the varietal forms already 

 described, it being understood, of course, that intermediate forms of all 

 grades of relationship are liable to be met with. What may perhaps be 



