218 PROCEEDINGS OF THE ACADEMY OF 



cusps on central and all the lateral teeth ; its centrals and late- 

 rals are not of the same shape as described above for H. Kelletti, 

 but resemble those of Polygyra, Stenotrema, and Triodopsis. Thus 

 in this as in other subgenera, we find the type of dentition not 

 constant in all the species. 



The long, narrow base of attachment and pj'riform reflection 

 of most of the species of Arionta agree with those of Hemitrochus 

 (see p. 181) more nearly than any other of our genera or subgenera, 

 but that genus has quite different marginal teeth. 



The dentition of H. arbustorum is alone known of the species 

 foreign to America, and that by a figure of Lehmann (Lebenden 

 Schnecken, pi. XL, fig. 29) too unsatisfatory to be of value for the 

 purpose of comparison. 



H. arrosa (pi. XIV., fig. 2), 54154 teeth. 17 laterals. 



H. Townsendiana (pi. XY1II., fig. 8) has 60160. Another 

 membrane had 40 1 40. 



H. tudiculata (pi. XIV., fig. 1), 50150, with 26 perfect late- 

 rals. 



H. Nickliniana (pi. XIV., fig. 8). 



H. Ayresiana (pi. XIV., fig. 6), 50 1 50, with 15 perfect laterals. 



H. redimita (pi. XIV., fig. 7). The 17th tooth has its inner 

 cutting point split. 43 1 43. 



H. intercisa, not examined. 



H. exarata (pi. XIV., fig. 10), 54 1 54, 19 perfect laterals. 



H.ramentosa (pi. XIV., fig. 9), 60 1 60, with 21 perfect late- 

 rals. The 18th tooth has the side cutting point. 



H. Calif orniensis (see L. and Frw. Sh., 1., p. 171, fig. 297). 

 Teeth 56156. 



H. (Jarpenteri. Too late for illustration, I have received speci- 

 mens collected by Mr. Henry Hemphill. There are 48 1 48 

 teeth, with 20 laterals ; the side cutting points are visible beyond 

 the 7th tooth. 



H. Mormonum, not examined. 



H. sequoicola (pi. XIV., fig. 5), 46 1 46, 18 perfect laterals. 



H. Diabloensis. 



Too late for illustration, I have received from Mr. L. Q. Yates 

 specimens of the form called Diabloensis by Dr. Cooper. There 

 are 37 1 37 teeth, with 17 laterals. There are side cutting 

 points beyond the 12th tooth. 



H. Traski (pi. XIV., fig. 4), 36136 ; the 13th tooth has the 

 wide cutting point; 16 laterals. 



