On Prophysaon^ etc, 299 



Animal limaciform, blunt in front, pointed behind. Man- 

 tle anterior, small, bhintij truncated before and behind, free 

 around its edges, containing a well defined, solid, testaceous 

 plate. A longitudinal furrow along the sides above the foot. 

 A distinct locomotive disk. Respiratory orifice at the poste- 

 rior third of the mantle, with a cleft to its risfht maro-in. 

 Anal orifice contiguous to the last, slightly below and behind 

 it. Orifices of generation on the right of the body, below 

 the anterior, free part of the mantle, distinct but contiguous 

 (in A. californicus, certainly), that of the male organ ante- 

 rior. Tail furnished with a perpendicular, triangular mucus 

 pore, with a horizontal mucus slit to the end of the tail. 



Testaceous plate fiat, thick, calcareous, simple, not spiral; 

 longer than wide, hexa<ronal. 



Jaw (see L. and F. W. Shells, p. 278, fig. 497) slightly 

 arcuate, with numerous (from eight to twenty in the several 

 species) stout, crowded ribs, denticulating either margin. 



Lingual membrane (see L. and F. W. Shells I, p. 279, 

 fig. 498) as usual in Helix. Teeth in numerous horizontal 

 rows ; centrals tricuspid ; laterals bicuspid ; marginals (see 

 our plate xiii, fig. 1) quadrate, irregularly denticulated, the 

 inner cusp the largest.* 



Inhabits the Pacific Coast of the United States, at least 

 from lat. 34° to 49°, apparently not eastward of the Sierra 

 Nevada and Cascade Ranges. 



The species on which the genus was founded has been 

 known for many years as a Litnax (see Gould in Terr. Moll. 

 U. S., II, III and Ex. Ex. Mollusca, where an additional 

 figure is given), but it was not until 1859 that Morch (Mai. 

 Blatt. VI, 110) recognized it to be distinct from Limax and 

 proposed a generic name, ArioUmax. In 1865, W. G. 

 Binuey (Amer. Journ. Conch. I, p. 48, pi. vi, figs. 11-13) 

 gave a more detailed generic description, adding figures of 



*In only one instance have we seen marginal teeth as in our figure. In all other 

 specimens examined the marginals are as figured in L. and F. W. Shells, I. c, with one 

 long cusp and one obsolete side cusp. 



