156 THE CHICAGO ACADEMY OF SCIENCES. 



form "is characteristic of the quitter waters of the long, narrow har- 

 bors which are such a remarkable feature of the island" (Walker). 

 Typical lilliance lives on a wave-beaten shore, and this precarious en- 

 vironment has caused the aperture to become enlarged to provide for 

 the larger foot to enable it to retain its hold on submerged objects. 

 The Isle Royale form, living in quieter water, has not developed the 

 large aperture of the Tomahawk Lake shell. 



The Tomahawk Lake shells vary to some extent, those inhabiting 

 the quieter bays having a longer spire and a smaller aperture. These 

 shells closely resemble the Isle Royale specimens and also clearly indi- 

 cate relationship with appressa. Specimens referable to apprcssa were 

 collected at one station in Tomahawk Lake, the habitat being marshy 

 in character. Some pathologic forms occur in the Wisconsin shells, 

 the abnormalities being confined principally to the last whorl and aper- 

 ture. Specimens from Lake Harriet, Minnesota, collected by Mr. L. 

 E. Daniels, are also referable to this race. In the course of time this 

 race will probably assume specific characteristics, a fact foretold by 

 its remarkable uniformity. 



The race is dedicated to my wife, Mrs. Lillian M. Baker, who 

 assisted in the discovery of the type specimens. 



Lymnaea stagnalis sanctaemariae (Walker). Plate XXI, figures 

 1-7; plate XXII, figures 7, 8; plate XXIII, figures 1-3. 



Limncea stagnalis sanctcemarice Walker, Nautilus, VI, p. 31, pi. 1, figs. 4, 5, 

 1892; Rev. Moll. Faun. Mich, pp. 7, 17, 1895. 



Lymncea stagnalis var. sanctcemarice Walker, An. Rep. Mich. Geol. Surv., 

 1908, p. 289, fig. 63, No. 2, 1909. 



Limncea stagnalis var. sanctcemarice Cockerell, Science Gossip, No. 388, 

 p. 27, Feb. 1893. 



Limncea stagnalis higleyi Baker, Nautilus, XVIII, p. 142, 1905. 



Lymncea stagnalis var. higleyi Walker, An. Rep. Mich. Geol. Surv. 1908, 

 p. 289, fig. 63, No. 5, 1909.— Gleason, 1. c, pp. 6-64, 1909. 



Limncea stagnalis var., Walker & Ruthven, Rep. Geol. Surv. Mich., 1905, 

 pp. 97, 98, 1906. 



Lymncea stagnalis var., Walker, An. Rep. Mich. Acad. Sci., 1908, p. 289, 

 fig. 63, Nos. 3, 6, 1909. 



Limncea jugularis Sowb., Conch. Icon., XVIII, Lim. pi. 4, fig. 24, 1872. 



Limncea stagnalis Adams, Rep. Geol. Surv. Mich., 1908, p. 10, 1909. 



Shell : Broadly ovate, with short spire and widely expanded 

 aperture, which is usually twice the length of the spire; spire whorls 

 flattened, producing a mammilliform appearance; spire rapidly accu- 

 minating ; whorls, 5j4 ; body whorl very large, rounded or even glob- 

 ular, slightly shouldered in some specimens ; aperture large, somewhat 

 flaring, expanded; axis typically strongly gyrate; the umbilical region 



