116 THE NAUTILUS. 



The figures on PI. Ill are from camera-lucida drawings all 

 magnified 10 diameters. The shells were selected for size only, 

 that is as near the same size as possible from material at hand, 

 and from localities as near together as I had them in my collec- 

 tion. Figs. 13 to 16 are large shells of each species. 



1 lamellidens Thunderhead, Gt. 



Smoky Mts Diana. 2.70 mm., Umbilicus .29 mm. i 



2 multidentata Oakdale, Morgan Co., 



Tenn " 2.70 " " .52 " J 



3 lamellidens Anderson, Franklin 



Co., Tenn " 1.96 " .29 



r 



4 multidentata Sherwood, Franklin 



I 



Co., Tenn " 2.19 " .15 



5 lamellidens Banners Elk, Wautauga -> 



Co., N. C " 2.40 " " .29 " 



6 multidentata Cranberry, Mitchell 



Co., N. C " 2.65 " " .46 " 



7 lamellidens Litchfield, N. Y . . . " 2.40 " " .29 " "I 



8 multidentata Litchfield, N. Y. . . " 2.53 " .46 " / 



9 lamellidens Deering, N. H. . . . " 2.13 " " .20 " 1 



10 multidentata Hoosic, N. Y. . . . " 2.53 " .46 " / 



11 lamellidens Norway, Me " 2.08 " .23 " 1 



12 multidentata Quebec, Can. ... " 2.70 " " .40 " / 



13 lamellidens No. 1, large shell . . " 3.90 " " .46 " 



14 multidentata Stevenson, Ala., large " 3.11 " " .69 

 15 lamellidens No. 1 same size as No. 



14 " 3.11 " .35 



16 multidmtata largest Quebec .... " 3.07 .63 " 

 17 lamellidens No. 1 same size as 7, 9 



and 11 " 2.21 " .29 " 



18 lamellidens No. 1 same size as 7, 9 



and 11 " 2.27 .29 " 



From the measurements given above it will be seen that in 

 shells of approximately the same diameter the umbilicus in 

 lamellidens is about three-fifths of the diameter of that of multi- 

 dentata, the single marked exception being Nos. 3 and 4. 



In figures 13, 14, 15 and 16, mature shells, it will be noticed 

 that in multidentata the umbilicus widens rapidly in the last 

 whorl while in lamellidens it does not. This can also be seen 

 in the other figures, but it is not so pronounced. 



