ARIONTA. 



369 



Fig. 250. 



A. Diablotnsis. 



Helix Diablocnsis, J. G. Cooper, Am. Journ. Conch., IV. 221, no descr. ; Cal. 



Proa, III. 260, descr. without name. 

 Lysinoe Diabloensis, J. G. Cooper, Proc. Acad. Nat. Sci. 



Phila., 1872, p. 150, PI. III. Tigs. G, 1 - 4. 



Californian Region, Mt. Diablo near San Francisco. 



Jaw, as usual ; 5 ribs. 



Lingual membrane (PI. IX. Fig. T) as usual in the genus. 

 The central and first lateral teeth have no side cusps or 

 cutting points ; these appear on the thirteenth. The eighteenth tooth lias its 

 inner cusp bifid; there may, therefore, be said to be 17 laterals. The mar- 

 ginals are low, wide, with one inner, long, oblique, bifid cutting point, and 

 one outer small cutting point. There are 37 — 1 — 37 teeth. 



Genitalia as in A. exarata. 



Dr. Cooper remarks: It is remarkable for having 7 whorls, while A. sequoi- 

 cola and A. Mormonum of the same size have but 6 ; it is also less com- 

 pressed than the latter, and the umbilicus is less covered. The color where 

 remaining is shining gamboge-yellow (faded), with a single very narrow band 

 above the middle, not showing the pale band on either side of it, which is so 

 marked in others of the genus. The sculpture seems to have been very slightly 

 indented, and with the faint lines of growth cut by smooth depressed waved 

 grooves transversely, and thus obliquely to the sutures (while those of A. 

 Traski are parallel). Greater diameter, 0.95 mill. ; height, 0.40 inch. Mt. 

 Diablo range. 



Arionta Traski, Newcomb. 



Shell umbilicated, globosely depressed, very thin, translucent, dark horn- 

 colored, with a revolving chestnut band, doubly edged with 

 white ; with delicate oblique striae and crowded micro- 

 scopic revolving lines ; spire hardly elevated, apex flat- 

 tened ; whorls 6, slightly convex, gradually increasing, the 

 last rather plane above, inflated below, not falling before, 

 banded above the middle ; umbilicus moderate, conical ; 

 aperture very oblique, lunately semicircular, banded with- 

 in ; peristome with a white thickening, regularly round- 

 ing, its terminations joined by a light transparent callus, 

 that of the columellar widened, subreflected, but not at 

 all covering the umbilicus. Greater diameter 21, lesser 

 16 mill. ; height, 9 mill. 



Helix TrasHi, Newcomb, Proc. Cal. Acad. Nat. Sci., II. 91 (1861). 

 Aglaja Traskii, Tryon, Am. Journ. Conch., II. 314, PI. V. Fig. 16 (1866). 



Los Angeles, California, in the Californian Region. 



The specimen figured was received from Dr. Newcomb. It may not be en- 

 tirely mature. 



vol. iv. 24 



Fig. 251. 



A. Traski. 



