380 A MANUAL OF AMERICAN LAND SHELLS. 



whorl. The internal revolving lamina easily distinguishes the species. 



Fig. 413 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 cut- 

 ting point and one short, bluntly bifid, small, outer cutting point (Terr. 

 Moll., V, Plate VI. Fig. K), all of same type as in septemvolva. 



Genitalia as in P. septemvolva. 



Polyifyra Carpenteriana, Bland. 



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

 Fig 414. obllqucly and acutely ribbed, beneath convex, slightly 

 striated, shining, often ornamented with indistinct white 

 spots ; suture deeply impressed ; whorls 5 J to 6^, the last 

 subangular at the periphery, shortly but suddenly de- 

 flected at the aperture, gibbous, scrobiculate, constricted, 

 tumid behind the aperture and ribbed, base dilated, with 

 a white, internal, thread-like lamina* on the columellar 

 wall near the point of attachment of the aperture ; aper- 

 ture very oblique, lunate; peristome callous within, 

 enlarged. ' thickcned, little reflected, the margins joined by a trian- 

 gular dentiform lamella. Greater diameter 10, lesser 9""" ; height, 4""", 



Helix microdonta, Pfeiffer, Mod. Hel. Viv., 499, ex parte? (1848). — W. G. Binney, 



Terr. Moll., iv, 91, pi. Ixxviii, fig. 28, excl. fig. 

 Helix Carpenteriana, Blaxd, Aun. N. Y. Lye, vii, 137. — W. G. Binney, L. & Fr.-W. 



Sh., i, 107, fig. 183 (1869). 

 Polygyra Carpenteriana, Thyon, Amer. Joiirn. Conch., iii, 159, pi. xi, fig. 24, not 23 



(1867).— W. G. Binney, Terr. Moll., v, 284. 



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

 part of the i)en insula and on the keys from Little Sarasota Bay to 

 Key Biscayne ; Lake Harvey. I have received fossil specimens im- 

 bedded in limestone rock. 



This species was formerly 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 abruptly contracted, becoming narrower 



* As in P. cereolus (see Fig. 413). 



