240 THE CHICAGO ACADEMY OF SCIENCES. 



BRITISH AMERICA. 



ONTARIO: Ottawa, Carleton Dist. (Heron); Carleton Co. (Walker). 



GEOLOGICAL RANGE: Unknown. 



ECOLOGY : Abundant in still water in sheltered borders of rivers, 

 in small brooks, ditches and streams and in shallow overflows. Clings 

 to dead leaves or other submerged debris or crawls over the muddy 

 bottom of its habitat, in shallow water. Associated with Galba obrussa, 

 Aplexa hypnorum and the small planorbes (Baker). In ditches and 

 brooks in pastures (True). Common in damp places and in ditches 

 along roads where water collects only in rainy weather (Ny lander). 



REMARKS: The shell of umbilicata may be distinguished from 

 cubensis by its smaller size, longer spire, less globose body whorl, 

 rounder spire whorls and by the less triangular and more erect inner 

 lip, which is peculiarly rolled over in cubensis. In half-grown speci- 

 mens the spire is a trifle shorter than the aperture, but in mature indi- 

 viduals the spire is as long, or even a trifle longer, than the aperture. 

 In umbilicata the center of rotundity of the body whorl is nearer the 

 anterior end than in cubensis, the latter being decidedly effusive an- 

 teriorly. Specimens are occasionally found with a pink columella. 

 Umbilicata differs from humilis in the shape of the inner lip, which 

 forms a broad, flat, rolled up shelf, while in humilis it is narrow and 

 the margin is rolled in instead of up. The shell of umbilicata is also 

 more elongate and regularly long-ovate than that of humilis. 



For the past eighteen or twenty years Adams' Lymnaa umbilicata 

 has been a puzzle to students of the Mollusca, and a number of very 

 diverse opinions have been published concerning it. By some it has 

 been considered a synonym of caperata, by others a variety of the same 

 species, and by a few a synonym of cubensis Pfeiffer. The history of 

 the treatment of umbilicata is interesting. Adams described the species 

 in 1840 in the American Journal of Science and figured it in the Boston 

 Journal of Science. Haldeman, in his monograph, in 1842, considered 

 it a synonym of caperata. The earlier students Lewis, Tufts, True, 

 Currier, Beauchamp, etc. considered it a distinct species. Tryon, in 

 his Catalogue (American Journ. Conch., 1, p. 255), placed it in the 

 synonymy of caperata. Binney placed it under caperata in his mono- 

 graph, but treated it as possibly distinct in Binney's Gould. Baker and 

 Daniels, in their papers on the Mollusca of Illinois and Indiana, have 

 considered it a variety of caperata with short spire and bulbous whorls. 

 Dall, in his Alaska Molluska, places it in the synonymy of caperata. 



In 1891, Pilsbry (Proc. Phil. Acad., 1891, p. 321) stated as fol- 

 lows : "The L. umbilicata C. B. Ad. is completely synonymous with 



