LYMNA:IDZ OF NORTH AMERICA. 289 
Lea’s type of plica is preserved in the Smithsonian Institution. 
The single specimen is undoubtedly the small form of obrussa herein 
described. Plica is described as imperforate, but the type has a very 
small chink which is emarginated by the inner lip, which is impressed 
in the manner shown on plate XXXII. Planulata, of which the type 
lot of six specimens is preserved, is also the same; this flattening of 
the whorls is well shown in figure 9 on plate XXXII. The type of 
exigua is not in existence. The three forms described by Lea, of which 
exigua is first mentioned, constitute a distinct and easily recognizable 
variety of obrussa. 
Galba obrussa decampi (Streng). Plate XXXII, figures 15-22. 
Limnea desidiosa var. decampi STRENG, Nautilus, IX, p. 123, text figure, 
March, 1906—WaALKER, Geol. Surv. Mich., VII, pl. 3, p. 101, 1903. 
Limnea desidiosa Baker, Journ. Cin. Soc. N.-H., XIX, p. 176, 1900.— 
NyLANbDER, Nautilus, XIX, p. 162, 1901. 
Lymnea obrussa decampi BAKER, Bull. Il. Lab. N. H., VU, p. 103, 1906. 
Lymnea obrussa var. decampii LERMOND, Shells of Maine, p. 37, 1908. 
SHELL: Small, oblong or subfusiform, somewhat inflated, sub- 
conic, rather solid; periostracum pale horn; surface rather dull, growth 
lines distinct but not coarse, spiral striation generally absent; whorls 5, 
rather rapidly enlarging, the spire whorls convex, and distinctly shoul- 
dered near the suture, the body whorl very much flattened in the 
middle; spire short, broadly conic, turreted, about as long as the aper- 
ture; nuclear whorls as in obrussa; sutures deeply impressed, forming 
a distinct shoulder; aperture very long and narrow, somewhat ellip- 
tical, rounded below and forming a prominent shoulder at the upper 
part; inner lip narrowly reflected, forming an expansion which is not 
much compressed at its junction with the parietal wall; the lower part 
of the inner lip stands quite erect; umbilical chink large and conspicu- 
ous, emargined by the inner lip. 
Length. Breadth. Aperture length. Breadth. 
5.00 2.50 aoe .... mill. Type 
11.00 5.50 6.00 2.75 “ Maine 
8.50 4.00 4.50 > 0nune ri 
10.00 5.00 5.25 250) Illinois 
9.75 5.25 5.50 2505.5 Michigan 
Types: Coll. L. H. Streng, Grand Rapids, Michigan; cotypes, 
Coll. Bryant Walker, Detroit, Michigan; Acad. Nat. Sci., Philadelphia, 
No. 67805. 
Type Locatity: Brook’s Lake, Newaygo County, Michigan. 
ANIMAL, JAW, RADULA and GENITALIA: Unknown. 
