244 GEOMITRA. 



Subgenus HETEROSTOMA Hartman, 1844. 



Heterostoma HARTMAN, Erd- und Siisswasser Gasteropoden der 

 Schweiz, mit zugabe einiger raerkwiirdigen exotischen Arten, p. 

 177, type H. semiteeta Hartm., pi. 62 (vii), f. 1-4, = H. pauper cula 

 Lwe. 



Shell small, planorboid, umbilicated, angular or keeled at periph- 

 ery, with 4 to 5 whorls, the last deflexed, abruptly contracted at the 

 aperture, the lip-edge thin and slightly expanded, continuous ; basal 

 lip strongly arcuate, with a heavy callous rib ivithin, which ends in a 

 tooth within the outer lip ; parietal wall elevated. Type G. pauper- 

 cula Lowe, pi. 68, figs. 16, 17, 18. 



The two species grouped here have been widely separated in for- 

 classifications. 



G. paupercula Lwe., iv, 35. G. coronata Desh., iv, 34. 



semiteeta Hartm. juliformis Lwe. 



tracheloides Mke. 



Subgenus GEOMITRA Swainson, 1840. 



Geomitra Sw., Malacology, pp. 166, 332, type H. tiarella. Coro- 

 naria LOWE, Ann. Mag. (2), ix, p. 117 for coronula and tiarella; P. 

 Z. S., 1854, p. 193, type tiarella (preoc.). Craspedaria LOWE, t. c. 

 p. 117, and P. Z. S., 1854, p. 192, type H. delphinula. 



Shell depressed or conoidal, solid, dull brown, rudely sculptured ;. 

 whorls of the spire plicate below the sutures, more or less keeled at 

 periphery ; base cylindrical, umbilicated, sculptured with granose 

 spiral cords. Aperture nearly round, very oblique, the peristorne 

 expanded, thin, continuous, solute, the parietal callus raised from 

 the preceding whorl. Type G. tiarella Webb & Berthelot, pi. 68, 

 fig. 6. (See also pi. 68, figs. 1-3, G. delphinula). 



Jaw (of tiarella) low, slightly arcuate, the anterior surface with 

 about 15 flat, broad, crowded ribs, scarcely denticulating the cutting 

 margin. (Binney). 



Radula with 12. 9. 1. 9. 12 teeth of same character as figured for 

 Plebecula lurida. 



Distribution, Madeira. This group is extremely peculiar in the 

 coarse spiral sculpture of the base, and the coronated whorls of the 

 spire. 



