424 THE CHICAGO ACADEMY OF SCIENCES. 



linian) and Boreal (Canadian) life zones and of the Canadian and 

 Upper Mississippian regions. It occurs in both the Great Lakes and in 

 the Mississippi River drainage. 



RECORDS. 

 UNITED STATES. 



MICHIGAN: Onekama, Manistee Co. (E. E. Hand); Crystal Lake, Benzie 

 Co. (Kirtland; Walker); Higgins and Houghton Lakes, Roscommon Co.; Pine 

 Lake, Marquette Co.; small lake on Beaver Island, Mackinac Co. (Walker); 

 Douglas Lake, Cheboygan Co. (Pease). 



MINNESOTA: Minnetonka Lake, Hennepin Co. (Helen Abbott); Eagle 

 Lake, Jackson Co. (Bailey; Stearns); Ottertail Creek, Ottertail Co. (Kenni- 

 cott) ; Clearwater Lake, Wright Co. (Sargent; Walton). 



WISCONSIN: First of four lakes, Madison, Dane Co. (Baker; Carpenter; 

 Chadwick; Letson Wis. Nat. Hist. Surv.) ; Kenosha, Kenosha Co. (Chadwick; 

 Wiswall). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY: Dr. R. J. Kirkland thus describes the habits of angu- 

 lata (mighclsi AUTHORS not BINNEY) : "I made a visit to Crystal 

 Lake, Benzie County, Mich., in July and again in October. Along the 

 shores are thousands of dead Limn&a mighelsi W. G. Binn., and 

 though many hours were spent in July in searching for living ones, 

 not one was found, until an improvised dredge brought them to view 

 from a depth of about twelve feet. Hiring a couple of men to row, 

 about two hundred were taken in half a day's work. This fall, how- 

 ever, I was surprised to see them in shallow water (one to three feet), 

 and I collected over a thousand by wading and picking them up one 

 by one. They were not in groups at all, but scattered irregularly in 

 patches over the bottom. Some of them were half buried in the sand 

 and the greater part resting with the head toward the shore, and where 

 a track was visible, it was a line from deeper to shallower water. 

 During the few days under observation, not a single individual was 

 seen floating on the surface." (Nautilus XIV, p. 8, 1900). 



Sargent records its ecology as follows: "Two quite distinct va- 

 rieties of texture were taken. One corneous, the other nearly white, 

 opaque and heavier, with much thickened margins. Both forms were 

 plentiful and near together. One was found on the pebbles, the other 

 on the sandy bottom." 



REMARKS: Angulata is very closely related to emarginata, the 

 chief points of difference being the solid shell, tightly closed umbilicus, 

 angulated whorls and depressed spire. 



Sowerby's description is as follows: "Shell solid, pinky brown, 

 rather square, spire short, whorls broad, angular, the last large ; straight 

 at the sides, excavated behind the columella; aperture subtrigonal, 



