OF NORTH AMERICA. 451 



SHELL: Rather thin, convex, tumid; periostracum white or pale 

 straw color ; surface dull, with fine growth lines and minute spiral lines ; 

 often malleated ; nuclear whorls as in emarginata; whorls 5 to 6 ; con- 

 vex; rapidly increasing in size, the body whorl very convex; spire 

 rather short, less than half the length of the shell, broadly acutely 

 pyramidal ; sutures impressed ; aperture ovate or elongate-ovate, some- 

 what expanded and produced in front; peristome thin, sharp, with a 

 light varix ; inner lip expanded to form a wide shelf which is reflected 

 over the body whorl, leaving a rather wide, umbilical chink ; the pariet- 

 al callus is quite erect in some specimens ; axis slightly twisted, but the 

 pillar of the aperture is without a fold. 



Length. Breadth. Aperture length. Breadth. 



37.00 23.00 22.50 13.00 mill. (Ball.) 



38.00 26.00 26.00 19.00 " 



23.00 15.00 15.00 8.00 " Isle La Crosse. 



18.50 13.00 11.25 7.25 " " 



TYPES: Smithsonian Institution, No. 180333, one specimen; No. 

 110376, two specimens figured by Dr. Dall, plate 1, figures 1, 2. 



ANIMAL, JAW, RADULA and GENITALIA: Unknown. 



RANGE: (Figure 50). Central Keewatin to Central Athabaska, 

 south to Manitoba. A species of the Hudsonian and Mackenzian re- 

 gions and of the Boreal (Canadian) life zone. 



RECORDS. 

 BRITISH AMERICA. 



ATHABASKA: Clear Lake, N. Lat. 56 (Dall) ; Isle La Crosse Lake (Ken- 

 nicott; W. A. Nason). 



KEEWATIN: Knee Lake, near 55 N. Lat. (Preble). 



MANITOBA: English River (Kennicott). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY: Not recorded. 



REMARKS : An examination of the type material has led the writer 

 to consider preblei a good species and not a variety of binneyi. It 

 will be recognized at once by its peculiar swollen form, raised in- 

 ner lip and deep umbilical chink. Dr. Dall suggested a resemblance to 

 L. megasoma and says this resemblance "is so marked that one wonders 

 whether some of the records of the latter species from high northern 

 localities may not have been based on specimens of this form." This 

 similarity is only apparent in one or two specimens. The two species 

 are totally unlike, particularly in color. Preblei is larger and thinner 

 than binneyi, the whorls are more tumid, the spire is more acutely 

 conical and the inner lip more erect and without a plait. Some ma- 



