394 THE CHICAGO ACADEMY OF SCIENCES. 



It was at first identified as niagarcnsis, but differs from that race in 

 having a more elongated shell, a longer spire and hence longer spire 

 whorls, and a more elongated and narrower aperture. The race is 

 so characteristic that it cannot be mistaken for any other species or 

 race. There is some variation in the shape and degree of impression 

 of the inner lip and also of the aperture, but on the whole the race is 

 unusually constant in general form. Several specimens have been seen 

 in which the upper part of the whorls is distinctly shouldered. 



The race is common on the St. Clair flats near Detroit. Walker's 

 Michigan reference (op. cit. p 291), in which he says, "Associated 

 with this form at Station IV, 6, (Small Island in Tobin Harbor, Isle 

 R ovale ) was a very thin, elongated form with the characteristic sculp- 

 ture of catascopium, which is closely related to. but much more fragile 

 than; the elongated form which is characteristic of the lower Great 

 Lakes," appears to be referable to this race. 



The race is named in honor of Prof. Chas. C. Adams, of the 

 University of Illinois, who has contributed many valuable notes to the 

 ecology* of Michigan Mollusca. 



Galba davisi (Walker). Plate XLI, figure 5. 



Lymncea davisi Walker, Nautilus, XXII, p. 17, pi. ii, figs. 9-10, June 1908. 



"Shell: Of medium size, globose-conic; perforate; light horn- 

 color ; whorls 5 ; the spire about one-third of the entire length of the 

 shell, rapidly acuminating and with a minute, sharp apex ; the whorls 

 of the spire are flattened and but slightly convex, with a distinct, but 

 not deeply impressed suture; body whorl large, inflated, ovate, flat- 

 tened above and rounded below ; lines of growth distinct, fine and regu- 

 lar, minutely decussated with revolving spiral lines ; aperture large, 

 pear-shaped, acutely angled above and broadly rounded below, about 

 three-fifths of the entire length, lip sharp, slightly thickened within, 

 straight above, somewhat expanded below, broadly reflected over and 

 nearly covering the small umbilical perforation ; columella with a very 

 slight fold ; axis rather thick, round, scarcely if at all folded." 



Length. Breadth. Aperture length. Breadth. 



15.20 7.50 9.00 4.00 mill. Type. 



15.00 7.50 9.50 4.50 " " 



Type : Collection Bryant Walker, Detroit, Michigan, two speci- 

 mens, Xo. 20092. 



Type Locality: Fish Point, Tuscola Co., Michigan. 



Animal, Jaw, Radula and Genitalia : Unknown. 



Range : Tuscola Co., Michigan. A species of the humid division 

 of the Transition life zone and of the Canadian region. 



