284 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



The umbilical opening, in specimens of about equal size, is only half the 

 width of that in septemvolva ; the last whorl is wider, especially towards its ter- 

 mination at the aperture, more inflated, and rather less acutely carinated. The 

 aperture is more orbicular, more contracted, and the peristonie more expanded 

 and acutely reflected, and at its junction below with its pillar lip more closely 

 appressed to the last whorl. 



Fig. 181 represents a specimen broken, so as to show the internal lamina. 



Jaw as usual ; 14 ribs. 



There are 22 1 22 teeth, with 9 laterals on the lingual membrane, the 

 inner cutting point of the tenth tooth being bifid. Marginals with base of 

 attachment low, wide, with one inner, long, oblique, bifid cutting point, and one 

 short bluntly bifid, small, outer cutting point (PI. VI. Fig. K), all of same type 

 as in septemvolva. 



Genitalia as in P. septemvolva. 



Polygyra Carpenteriana, BLAND. 



Shell umbilicate, orbicular, horn-colored or pale rufous, above flat, obliquely 

 and acutely ribbed, beneath convex, slightly striated, shining, 

 often ornamented with indistinct white spots ; suture deeply 

 impressed ; whorls 5^ to 6^, the last subangular at the periph- 

 ery, shortly but suddenly deflected at the aperture, gibbous' 

 scrobiculate, constricted, tumid behind the aperture, and 

 ribbed, base dilated, with a white internal thread-like lamina 1 

 on the columellar wall near the point of attachment of the 

 aperture; aperture very oblique, lunate; peristome callous 

 within, thickened, little reflected, the margins joined by a 

 triangular dentiform lamella. Greater diameter 10, lesser 9 

 mill. ; height, 4 mill. 



P CfcrTT ' r ' Helix microdonta, PFEIFFER, Mon. Hel. Viv., 499, ex parte ? 



enlarged." (1848). W. G. DINKEY, Terr. Moll., IV. 91, PI. LXXVIII. 



Fig. 28, excl. fig. 

 Helix Carpenteriana, BLAND, Ann. N. Y. Lye., VII. 137. W. G. BINNEY, L. 



& Fr.-W. Sh., I. 107, Fig. 183 (1869). 

 Polygyra Carpenteriana, TRYON, Amer. Journ. Conch., III. 159, PL XL Fig. 24, 



not 23 (1867). 



In the Florida Subregion on the mainland of the extreme southern part of 

 the peninsula and on the Keys from Little Sarazota Bay to Key Biscayne. I 

 have received fossil specimens, imbedded in limestone rock. 



This species has been hitherto named microdonta in American cabinets. It 



is readily distinguished from all the other species of the group by its strong 



acute rib-like striae, and the peculiarity of the outer whorl. About the last 



third of it, behind the aperture, is ribbed and tumid ; the whorl is then rather 



1 As in H. cereolus, see Fig. 181, p. 283. 



