GASTROCOPTA, NORTH AMERICA, WEST INDIES. 21 



is from a single specimen, there may be some variation. Other 

 parts could not be examined" (Sterki). 



Distribution. Tennessee: Knoxville (type loc., Mrs. Geo. 

 Andrews) ; Fayetteville (B. Walker coll.) ; Columbia (B. 

 Shimek, A. A. Hinkley). Alabama: Gurley and Huntsville 

 (H. H. Smith). Michigan: Grand Eapids (B. Walker). In 

 most lots it was associated with G. armifera. 



Bifidaria clappi STERKI, Nautilus, XXII, Feb. 1909, p. 108, 

 pi. 8, fig. 4. 



The chief differential character of this race is in the shape 

 of the columellar lamella. In a profile view (pi. 1, fig. 8) it 

 is seen that the plane of the lamella is straight very nearly to 

 the base, while in armifera the greatest projection forward is 

 well above the base. The anterior branch of the columellar 

 lamella, which is more or less apparent in armifera, is want- 

 ing in clappi, being concrescent with the lower end of the 

 main lamella (compare figs. 4 and 8). In view of the varia- 

 bility of the columellar lamella in armifera, it does not ap- 

 pear to me that this small modification is of specific impor- 

 tance. Figured from co-types, one of which (fig. 7) served 

 for the original figure of the species (no. 98279, A. N. S. P.). 



Dr. Sterki writes: "The species shows little variation, ex- 

 cept in altitude, with nearly the same diameter, and such as 

 are noted in the description. There is no tendency towards 

 having the peristome continuous. . . . B. clappi is remarkable 

 for its resemblance to some forms of B. armifera Say, for a 

 variety of which it has been taken. Yet it is quite distinct. 

 Of over 150 specimens carefully compared with more than 

 1500 armifera, not one was found doubtful or intermediate. 

 The most tangible difference is in the shape of the columellar 

 lamella. The shell averages somewhat smaller, the apex is 

 more acute, the surface striae are finer and slighter, the lower 

 palatal plica is always regular." 



Series of G. contracta. 



The angular and parietal lamellae are completely concres- 

 cent, the parietal being abruptly bent towards the periphery 

 within, and usually has a low, further continuation inward; 

 inner end of the columellar lamella curving down. 



