ARIONTA. 



353 



aperture, granulated, finely striate and hirsute; spire subpyramidal ; whorls 6, 

 slightly convex, the last carinated at its middle, inflated 

 below, slightly descending; aperture oblique, lunate, sub- Fig. 236. 



angulate, white and banded within ; peristome white, 

 thickened, reflected, partially concealing the open um- 

 bilicus, ends approached. Greater diameter 25, lesser 19 

 mill.; height, 10 mill. 



Helix Hillcbrandi, Newcomb, Proc. Cal. Acad. Nat. Sci., 



III. 115, 181 (1864). — W. G. Binney, L. & Fr.-W. Sh., 



I. 163, Fig. 281 (1869). 

 Aglaja Hillcbrandi, Tryon, Am. Journ. Conch., II. 310, 



PI. V. Fig. 7 (1866). 



Tulumne County, California Region; also near Mariposa. a. HUUbrandL 



The specimen figured is from Dr. Newcomb. 

 Animal unobserved. 



Fig. 237. 



ARIONTA, Leach. 



Animal heliciform, mantle subcentral ; other characters as in Patula. Pro- 

 vided with a thick, white epiphragm. 



Shell umbilicately perforate, conic- or depressed-globose, thin; whorls 5-6, 

 the last gradually descending; aperture lunate-rotund; peristome broadly labi- 

 ate, its margins parallel, the basal dilated, often covering the umbilicus. 



The genus is almost exclusively confined to the California Region of our 

 limits. There is, however, one Mexican species, one African, and one Euro- 

 pean, A. arbustorum. The jaw of the last agrees with that of our species. 



Jaw thick, high, arched, ends but little attenuated, blunt ; cutting margin 

 without median projection ; anterior surface with a few, separated, stout ribs, 

 deeply denticulating either margin, and so disposed as 

 to leave each end of the jaw free from ribs. I have 

 counted 6 ribs on the jaw of arrosa; 9 in Townsendi- 

 ana ; 6 in tudicnlata ; 4 in Dupetuhouarsi ; 6 in Nickli- 

 niana; 6 in redimita; 6 in exarata ; 5 in Diabloensis; 

 about 7 in Carpenteri ; 3 in ramentosa; 5 in Ayresiana ; 

 5 in Californiensis ; 4-6 in sequoicola ; 8 in Traski; 8 in facta; 6 in Kelletti ; 

 7 in Carpenteri ; 9 of unequal size in Stearnsiana. The jaw of ruficincta differs 

 in having over 10 ribs covering its whole surface, and in being only slightly 

 arcuate. 

 I have not examined intercisa. 



The lingual membrane is long and narrow, arranged as in Patula. The 



characters of the individual teeth are shown in my plates. In Fig. O, P, 



R, S, and U, the gradual change from central through laterals to the extreme 



marginals is shown. The central teeth have a base of attachment much longer 



vol. iv. 23 



Jaw of A. arrosa. 



