OF NORTH AMERICA. 397 



Galba nasoni (Baker). Plate XLII, figures 14-17. 



Lymn&a nasoni BAKER, Trans. Acad. Sci. St. Louis, XVI, p. 12, pi. 1, figs. 

 1-4, May, 1906. 



SHELL: Rather small, globosely inflated, solid; periostracum 

 whitish, tinged with purple ; surface dull, marked by rather coarse 

 growth lines crossed by fine, impressed spiral lines; nuclear whorls 

 small, rounded, very wide and low, flattened, dark brown in color; 

 (plate XLIX, figure 0) ; whorls four, roundly inflated, tumid, the body 

 whorl very large and bulbous; spire much depressed, very broadly 

 acute; sutures slightly impressed; aperture broadly ovate, almost 

 round in some specimens, sometimes somewhat expanded, rounded 

 anteriorly, somewhat acutely angled posteriorly ; outer lip with a bluish- 

 white, longitudinal varix bordering its edge; inner lip narrow, ap- 

 pressed to the axis, leaving a very small chink and forming a distinct, 

 ascending plait on the columella; the inner lip slightly emargins the 

 umbilical chink; the callus on the parietal wall is thin; the interior 

 of the aperture is brown in color. 



Length. Width. Aperture length. Width. 



10.50 6.75 7.00 4.25 mill. Type. 



9.50 6.00 7.00 5.00 " 



8.50 6.00 6.25 4.00 " 



10.00 6.75 7.00 5.00 " " 



TYPES: The Chicago Academy of Sciences, four specimens, No. 

 23788. Cotypes, collection Illinois State University and Mr. Bryant 

 Walker, Detroit, Michigan. 



TYPE LOCALITY : Thunder Bay Island, near Alpena, Michigan. 



ANIMAL, JAW, RADULA and GENITALIA: Unknown. 



RANGE: Michigan. A species of the Boreal life zone and of the 

 Canadian region. 



RECORDS. 



MICHIGAN : Thunder Bay Island, near Alpena, Alpena Co., Michigan 

 (Nason). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY : Exposed shore of Lake Huron, where the water is 

 daily forced into the pools (Nason). 



REMARKS: Nasoni may be known by its small size, its short, 

 bulbous, dome-shaped spire and wide-spreading aperture. It somewhat 

 resembles certain forms of catascopium found in Pine Lake, Charle- 

 voix, Michigan, but differs in the very short spire, broad and tumid 

 last whorl, and in having one whorl less. The columellar plait is 

 also more distinct. Woodruffi has a differently shaped shell and a 

 totally different inner lip. Galba apicina is liable to be confused with 



