NATURAL SCIENCES OF PHILADELPHIA. 201 
Lingual membrane with 14—1—14 teeth, 5 laterals. All the 
teeth like those of H. labyrinthica (pl. X VIII., fig. 11). 
There are no known species foreign to North America, with 
which to compare the dentition and jaw of labyrinthica and 
Hubbardi. | 
Subgenus PoLyGyRa. 
Jaw high, arcuate, ends scarcely attenuated, blunt, cutting edge 
without median projection; anterior surface with numerous stout, 
separated ribs, denticulating either margin. I have 
counted 8 ribs in H. ventrosula; 14 in pustula; over 
: my, 14 in cereolus; 10 in espiloca; 13 in uvulifera; 10 
Uy i in Texasiana; 12 in Troostiana; 11 in leporina; 15 
Jaw of Helix in Mooreana; 20 in fastigans ; 7 in septemvolva; 10 
ventrosula. in Febigert; in Hazardi, auriculata, and auriformis 
they are alsonumerous. I have had no opportunity of examining 
the jaw in the other species found within our limits, Postelliana, 
avara, Hindsi, triodontoides, tholus, hippocrepis, oppilata, Dor- 
fewuilliana, Ariadne, cereolus (see p. 203), Carpenteriana (see ib.), 
pustuloides. 
By the character of its jaw, Polygyra can be compared only to 
Triodopsis and Mesodon among the other North American sub- 
genera of Helix. No foreign species has yet been examined. The 
genus is almost exclusively North American, though several species 
have been described from the West Indies and Mexico, and one 
from Bolivia. 
Fig. 46 shows the general arrangement of the teeth upon the 
Lingual dentition of Helix aurtformis? ([Leidy.] 
lingual membrane, the characters of the individual teeth being 
better shown in my plate VIII. The teeth do not differ from what 
I have described under Stenotrema (see p. 205). As inall the sub- 
genera, there is considerable difference in the length of the base: 
of attachment on the central and lateral teeth in the several 
species. 
The marginals are lower and wider (see pl. VELI.,.fig..1, d) than. 
14 
