POLYGYRA. 287 



Jaw as usual; 14 crowded ribs. 



P. pustula (PI. VI. Fig. E) has 17 — ^1 — 17 teeth on its lingual membrane, 

 with 8 laterals. 



Polygyra pustuloides, Bland. 



Shell widely umbilicate, planorboid, thin, rufous or pale horn-colored, deli- 

 cately striated, with thin, sparingly hirsute epidermis ; spire scarcely elevated ; 

 whorls 4 to 4^, slightly convex, gradually increasing, the 

 last subangular at the periphery, at the aperture gibbous, ^'^* ^^^ 



constricted, suddenly deflected, beneath devious ; suture 

 rather deeply impressed ; umbilicus wide, equal to one-third 

 of the larger diameter of the shell, showing all, but espe- 

 cially the penult whorl; aperture with an internal, fulcrum- 

 like process on the base of the shell, oblique, crescentic, 

 with an erect, oblique, white, parietal lamelliform tooth, 

 joined to the upper angle of the aperture by a slightly arcu- p pustuloides. 



ate, filiform callus ; peristome reflected, with margins ap- 

 proaching, and having two dentiform lobes separated by a deep fissure. 

 Greater diameter 5^, lesser^4^ mill. ; height, 2^ mill. 



Helix pustula, Binney, Terr. Moll, II. 201, PL XXXIX. Fig. 3, not of F^rus- 



SAC. 



Helix pustuloides, Bland, Ann. N. Y. Lye, VI. 350, Fig. 3 (1858). —W. G. 

 Binney, Terr. Moll., IV. 93 ; L. & Fr.-W. Sh., I. 110 (1869). 



Dccdalochila 2}ustuloides, Tryon, Am. Journ. Conch., 111. 61 (1867). 



Georgia and Alabama. A species of the Southern Region. 



P. pustuloides is intermediate in size between pustula and leporina, — is less 

 globose than the former, and more sparingly hirsute. It differs widely from 

 both in the character of the umbilicus ; the aperture is much like that of pus- 

 tula, but more narrow than that of leporina. The inferior tooth on the peri- 

 stome is more developed laterally than in jmstula, — indeed, it has a somewhat 

 bifid appearance, in which respect it is more allied to leporina. 



The fulcrum in pustuloides is of the same nature as that in leporina, but less 

 developed, and with the outer edge entire. 



As to the station of the species, I coj^y the following from one of Dr. Wil- 

 son's interesting letters from Darien, Georcjia : — 



" The place has an eastern exposure to the sea, high tides rising to the base 

 of the low bluff where they exist. The growth of trees, which consists mostly 

 of live oak and Celtis occidentalis, has never been cleared off'; the Palmetto scr- 

 rulata flourishes as an undergrowth. The soil is covered for a few inches in 

 depth with oyster-shells thrown there by the Indians, and decayed leaves and 

 fragments of branches are of course over all these, under which, and among the 

 superficial oyster-shells, the Helices live. P. pustula is nowhere near, or at 

 least a rigid search did not reveal any. Macrocyclis concava (dead) occurs in 

 small numbers, Triodopsis injiecta abundantly." 



