LYMN^ilD.E 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. 



Limncea desidiosa var. decampi STRENG, Nautilus, IX, p. 123, text figure, 

 March, 1906. WALKER, Geol. Surv. Mich., VII, pi. 3, p. 101, 1903. 



Limncca desidiosa BAKER, Journ. Cin. Soc. N. H., XIX, p. 176, 1900. 

 NYLANDER, Nautilus, XIX, p. 162, 1901. 



Lymncea obrussa decampi BAKER, Bull. 111. Lab. N. H., VII, p. 103, 1906. 



Lymncra 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 .... .... mill. Type 



11.00 5.50 6.00 2.75 " Maine 



8.50 4.00 4.50 2.00 " " 



10.00 5.00 5.25 2.50 " Illinois 



9.75 5.25 5.50 2.50 " Michigan 



TYPES: Coll. L. H. Streng, Grand Rapids, Michigan; cotypes, 

 Coll. Bryant Walker, Detroit, Michigan ; Acad. Nat. Sci., Philadelphia, 

 No. 67805. 



TYPE LOCALITY : Brook's Lake, Newaygo County, Michigan. 

 ANIMAL, JAW, RADULA and GENITALIA: Unknown. 



