GASTROCOPTA, NORTH AMERICA, WEST INDIES. 17 



1, figs. 3, 4, but usually it is less conspicuous, as in fig. 1. 

 Shells agreeing well with the types are to be found over 

 nearly or quite the whole range of the species, but there are 

 also several incipient races which have been defined by Dr. 

 Sterki. The most tangible differential features of these races 

 are found in the shape of the columellar lamella, of which 

 comparable views are given on pi. 1, figs. 3, 9, 11, and pi. 2, 

 fig. 3. The small differences in details of the palatal plicae, 

 shown in the several face views, are not of much significance,, 

 since these plicae are somewhat variable in most lots. 



la. Form interpres Sterki. 



"Near the typical form, generally somewhat slender; in- 

 ferior columellar lamella rather high up ; the base is narrow 

 inside and more keel-like outside; the aperture is narrowly 

 rounded at the base, and from this feature specimens are 

 easily recognized. More than any other form this shows 

 clearly that the so-called 'basal' is really an inferior colu- 

 mellar. 



"Distribution: Southern, especially southwestern; it ap- 

 pears to be the prevalent form in Kansas, Arkansas, Okla- 

 homa, and thus represents a geographical variety" (Sterki). 



This form is so intimately related to the typical armifera 

 that I am unable to segregate it. 



Ib. Form similis Sterki. PI. 1, fig. 6. 



"Averaging somewhat smaller; more cylindrical, often 

 more or less conical; whorls less convex; surface striae 

 slighter ; shell generally more milky- whitish, as noticed espec- 

 ially when a number of each, armifera and similis, are placed 

 side by side; peristome never continuous, somewhat less 

 everted; the columellar lamella is slighter, generally more 

 protracted downward, the lower palatal is shorter, sometimes 

 quite short; the spur of the parietal is larger" (Sterki). 



Distribution. Northern New York to Iowa, Minnesota, 

 Ontario. 



This is very close to armifera, the columellar lamella being 

 practically the same in form, but the margins of the peri- 

 stome are separated rather widely above. Figured from a 

 paratype from Rose Hill, Ontario, the type locality. 



