ARIONTA. 371 



The genitalia are like those of sequoicolu. The penis sac is, however, more 

 slender. There does not appear any retractor muscle of the penis sac. The 

 oviduct is greatly convoluted. 



Arionta ruficincta, NEWCOMB. 



Shell depressed-globose, umbilicated, rather thin, smooth, surface scarcely 

 broken by incremental stria?, with occasional revolving lines, 

 horn-color, with a median, revolving dark brown band, mar- 

 gined with white ; spire little elevated ; whorls 5 to 6, scarcely 

 convex, the last flattened-globose, descending at the aperture, 



convex below: aperture banded within, oblique, roundly lunate: 



A. nificincta. 



peristome white, thickened, its inner margin obtusely rounded, 



the right portion straight, basal and columellar portions reflected, partially 



concealing the umbilicus. Greater diameter 17, lesser 14 mill.; height, 9 



mill. 



Helix rufodncta, NEWCOMB, Proc. Cal. Acad. Nat. Sci., III. 117(1864). W. 



G. BINNEY, L. & Fr.-W. Sh., I. 174, Fig. 303 (1869). 

 Aglaja rufodncta, TRYON, Am. Journ. Conch., II. 315, PL VI. Fig. 20 (1866). 



San Diego and Catalina Island, California, in the Calif ornian Region. 



There is a form from Santa Barbara Island with thick shell and closed um- 

 bilicus. Greater diameter, 31 mill. 



Jaw more like the type common in Mesodon than in Arionta, that is, arcuate 

 rather than arched, margins rather pectinated than scalloped by the ends of 

 the ribs, which are about 10 in number. 



Lingual membrane (PI. IX. Fig. N) as usual in the subgenus, with 35 1 

 35 teeth, and 18 laterals, the nineteenth tooth having the inner cutting point 

 split. Another membrane has a side cutting point on all the laterals. 



I have examined two individuals, whose genital systems vary considerably. 

 That figured on PL XIV. Fig. B has a dart sac, but none of the other peculiar 

 accessory organs of Arionta. That figured PL XV. Fig. O (from Catalina 

 Island) has from one side of the base of the dart sac (x) a thread-like connec- 

 tion (2) with the base of the penis sac, and on the other side of the base of the 

 dart sac the peculiar accessory organ y. These accessories to the dart sac are 

 somewhat like those found in Slearnsiana. 



Arionta Gabbi, NEWCOMB. 



Shell subperforate, depressed-globose, thin, smooth, very delicately striated, 

 dirty white, darker above, with a median revolving, white-margined brown 

 band ; spire little elevated ; whorls 5, rather convex, the last tlattened-globose, 

 descending at the aperture; aperture lunately rounded, oblique; peristome 

 white, thickened, somewhat reflected, the columellar portion almost covering 

 the umbilicus. Greater diameter 10, lesser 8 mill.; height, 5 mill. 



