194 PROCEEDINGS OP THE ACADEMY OF 



Ariolimax Calif ornicus (pi. V., fig. 1) has the same type of 

 dentition, but the bases of attachment are more developed, and 

 are produced beyond the reflection at their upper margin. There 

 are 80 1 80 teeth, with 9 perfect laterals. 



Ariolimax niger, also (pi. Y., fig. 3), has the same type of den- 

 tition as A. Columbianus, the side cusps of the centrals are, how- 

 ever, more developed. On one specimen I found marginal teeth 

 with one inner stout, short, rounded cutting point, and two shorter, 

 rounded, side cutting points (see fig. 2), instead of the usual long 

 cutting point. This is the only variation in the dentition of the 

 genus which I have noticed. 



Since the above was written, I have received specimens which 

 agree with Cooper's description of Avion Andersoni, which appear 

 to be a true Ariolimax. Full descriptions will be given at another 

 time. The jaw has 13 ribs. The lingual membrane has 48 1 48 

 teeth of the type usual in the genus. 



Ariolimax Hemphilli, a species from Niles Station, Alameda 

 County, California, which I am about to describe under the name 

 of its discoverer, has a jaw with 8-12 ribs. Lingual membrane 

 with 31 1 31 teeth of the type common to the genus. 



For full remarks on this genus, see Proc. Ac. Nat. Sc. Phila. 

 1874, p. 33. 



The genus, as far as now known, is restricted to this country ; 

 there are, therefore, no descriptions or figures of the jaw and den- 

 tition of foreign species to compare with ours. 



Genus PROPHYSAON, Bl. and Binn. 



Jaw of the single species known, P. Hemphilli, thick, low, wide, 

 slightly arcuate, with but little attenuated ends, cutting margin 

 without median projection ; anterior surface with fifteen stout, 

 irregularly developed, separated ribs, denticulating either margin 

 (pi. XVL, fig. 9). 



Lingual membrane (pi. V., fig. 4) long and narrow. Teeth 

 about 40 1 40, with 16 perfect laterals. Centrals with a base 

 of attachment longer than wide, reflection extending less than one- 

 half the length of the base, with a very stout, short median cusp, 

 bearing a stout, short, blunt cutting point, and on either side a 

 subobsolete cusp bearing a stout, bluntly rounded, short cutting 

 point. Laterals like the centrals, but unsyrametrical, as usual, by 

 the suppression of the inner side cutting point and inner lower, 



