324 



A MANUAL OF AMERICAN LAND SUELLS. 



Fig. 349. 



Jaw of Pupa pentodon. 

 (Morse.) 



Jaw slightly arcuate, of uniform breadth, auterior surface longitud- 

 inally striate, concave margin minutely notched. 

 Lingual membrane with 64 rows of 21 (10-1-10) 

 teeth ; centrals with three subequal, very small 

 cusps 5 laterals bicuspid ; marginals serrate, the 

 inner point much developed. 

 Tlii.s is a very varial'le species. The ordinary specimeus vary chiefly 

 v^''- :i'"- in tlie armature of the aperture, the mar- 



ginal internal rim of calcareous matter 

 thickening with age and developing more 

 numerous denticles. The Ohio specimens 

 Liugu.i dentition of Pupa pentodon. ^Te of morc thau Ordinary size, clean and 

 shining, and were the form designated by Professor Adams as P. Tap- 

 paniana. Those found in Massachusetts are considerably smaller, cov- 

 ered with a well-developed epidermis, and often, if not always, have 

 tne aperture decidedly modified in form, being more triangular, and 

 the denticles more or less curved. To these was applied the name 

 curvidens ;* and the modifications are so constant as to incline us still 

 to regard them as constituting a distinct species. With all its varia- 

 tions, it has an aspect which enables us readil^^ to separate it from all 

 other species. The form of the shell itself and its semicircular aper- 

 ture are sufficiently peculiar. A more careful examination of the animal 

 shows decidedly that it does not belong to Vertigo, as supposed by Mr. 



Say. 



Subgenus LEUCOCHILA, Alb. & Mart. 



Animal as in Pupilla. 



Shell rimate, cyliudrically ovate, apex rather obtuse, rather smooth, 

 shining, pellucid ; whorls G-7, rather convex, aperture semi-oval, eden- 

 tulate or narrowed by folds, among which the parietal is the strongest; 

 peristome thickened, reflected, its external margin decidedly arcuate. 



Pupa fallax. Say. 

 Shell fusiform, regularly diminishing in volume from the body-whorl 

 riG. 351. to the apex, smooth; epidermis brownish horn-color; 



whorls G, very convex, stricTS of growth hardly apparent; 



suture well impressed ; aperture lateral, rounded-oval ; 



l)eristome white, rather broadly reflected, lined within 



with white callus, its right termination strongly curved ; 



umbilicus perforated. Length, 5i"""; diameter, 2-2^'""'; 



ai)erture, If"'"' long. 



* See figure 347, ante. 



Pupa fnllnz, 

 eulaigeil. 



