918 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 pyriform reflection 
of most of the species of Arionia 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, pl. XI., fig. 29) too unsatisfatory to be of value for the 
purpose of comparison. 
H. arrosa (pl. XIV., fig. 2), 54—1—54 teeth. 17 laterals. 
H. Townsendiana (pl. XVIII, fig. 8) has 60—1—60. Another 
membrane had 40—1—40. 
H. tudiculata (pl. XIV., fig. 1), 50—1—50, with 26 perfect late- 
rals. 
H. Nickliniana (pl. XIV., fig. 8). 
HI. Ayresiana (pl. XIV., fig. 6), 50-——-1—50, with 15 perfect laterals. 
H. redimita (pl. XIV., fig. 7). The 17th tooth has its inner 
cutting point split. 43—1—43. 
H. intercisa, not examined. 
H. exarata (pl. XIV., fig. 10), 54—1—54, 19 perfect laterals. 
H. ramentosa (pl. XIV., fig. 9), 60 —1—60, with 21 perfect late- 
rals. The 18th tooth has the side cutting point. 
H. Californiensis (see L. and Frw. Sh., l.; p. 171, fig. 297). 
Teeth 56—1—56. 
H. Carpentert. 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 Tth tooth. 
H. Mormonum, not examined. 
H. sequoicola (pl. XIV., fig. 5), 46—1—46, 18 perfect laterals. 
H. Diabloensis. 
Too late for illustration, I have received from Mr. L. G. 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 (pl. XIV., fig. 4), 36-—-l1—36 ; the 13th tooth has the 
side cutting point; 16 laterals. 
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