92 



LAND AND FRESH-WATER SHELLS OF N. A. [PART T. 



peristome is armed with a hook as in the other species, but is 

 narrower, less deeply seated, and more erect ; the inferior one is 

 rather a distinct tooth than a laraellar fold. The parietal process 

 differs entirely from that of H. auriculata, as plainly shown in 

 the figure. H. avar-a is without the groove on the last whirl 

 which prevails in auriculata, and the forms represented by Dr. 

 Binney as varieties of it. It is very rare in collections : I know 

 of but two specimens of it. 



Helix ventrosula, Pfeiffek. — Shell rimately perforated, globosely 

 depressed, thin and shiuiiig, pellucid, delicately striated, horu-colored ; spire 

 slightly raised ; whirls five, but little convex, the last one subangulated 

 above, falling suddenly towards the aperture, inflated below, anteriorly 

 gibbous and contracted ; aperture very oblique, ringeut ; peri- 

 stome acute, broadly reflected, its terminations scarcely ap- 

 proaching each other, but joined by two white, elevated 

 laminse, which are placed at acute angles on the parietal 

 wall ; the basal margin is also furnished with two white acute 

 denticles ; on the right margin is placed a white sub-perpen- 

 dicular, extended lamina. Greater diam. 13, lesser 11 ; height 

 V> mill. 



Helix ventrosula, Pfeiffer, Proc. Zool. Soc. 1845, 131 ; Mon. Hel. Viv. I, 

 417; in Chemkitz, ed. 2, I, 373 (1846), pi. Ixv, f. 5, (J (1849).— 

 Reeve, Con. Icon. no. 687 (1852).— W. G. Binney, Terr. Moll. IV, 

 73, pi. Ixxvii, f. 14. 

 Dcedalochila ventrosula, Tbyon, Am. Journ. Conch. Ill, 63, pi. x, f. 35, 

 39 (1867). 



Texas and Mexico. The specimen which furnished Figs. 1G5 

 and 166 is from the Sierra Madre. 



Jaw strongly arcuate, of uniform width, ends 

 blunt, anterior surface with broad ribs, crenulating 

 both margins. 



Lingual membrane with 93 rows of 24 — 1 — 24 

 teeth each ; centrals tricuspid, the side cusps very 

 small ; laterals of same shape, but bicuspid ; uncini 

 irregularly and bluntly serrate. 



Fig. 166. 



Fig. 165. 



Jaw of Helix 

 ventrosula. 



Lingual dentition of Hdix ventrosula. 



