. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. Jaw of S. ventrosula. Jaw high, arcuate, onds scarcely altenuated, blunt, cutting edge witliout median projection; anterior surface with numerous stout, separated ribs, den- ticulating either nian^in. 1 have counted 8 ribs in P. ventrosula; 14 in pus- lula; 10 in aurlrulata; 12 in PoHteUiana; 12 in Carpenteriaua; 10 in pusfrcloides; 12 in avai'a : over 14 in cereolus; 10 in espi- ; 13 in uvuUfera; 10 in Texasiana Sixid triodonlaides: 12 in Troostiana; 11 \\\ leporina; 15 in Mooreana; 20 in fasligdns : 7
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology; Zoology. Jaw of S. ventrosula. Jaw high, arcuate, onds scarcely altenuated, blunt, cutting edge witliout median projection; anterior surface with numerous stout, separated ribs, den- ticulating either nian^in. 1 have counted 8 ribs in P. ventrosula; 14 in pus- lula; 10 in aurlrulata; 12 in PoHteUiana; 12 in Carpenteriaua; 10 in pusfrcloides; 12 in avai'a : over 14 in cereolus; 10 in espi- ; 13 in uvuUfera; 10 in Texasiana Sixid triodonlaides: 12 in Troostiana; 11 \\\ leporina; 15 in Mooreana; 20 in fasligdns : 7 in septemvolca; 10 in Febifjeri; in Hazardi and aurlformts they are also numerous. I have had no opportunity of examin- ing the jaw in the other species found within our limits Hindsi, tholus, hippocrepis, oppilata, DorfeuilLiana, Ariadnce, By the character of its jaw, Pobjgyra can be compared only lo Triodopsis and Mesodon among the other North American subgenera of Helix. No foreign species has yet been examined. Fig. 158 shows the general arrangement of the teeth upon the lingual mem- brane, the characters of the individual teeth being better shown in my PI. VI. Fig. Lingual dentition of P. auriformis ? (Leidy). The teeth do not differ from wliat I have described under Stenotrema (see below). As in all the subgenera, there is considerable difference in the length of the base of attachment on the central and lateral teeth in the several species. I find considerable difference between the various species in the manner in which the lateral teeth pass into the marginals. In auriformis, Postelliana, espiloca, and Hazardi, the change is made simply by the greater development of the inner cutting point, not by its bifurcation (see PI. VI. Fig. N). In these species it is only the extreme outer marginals that have their inner cutting point bifid; in auriformvi a very few extreme marginals have a bifid cutting point. This species has very long inner cutting points to its margina
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Keywords: ., bookauthorha, bookcentury1800, bookdecade1860, booksubjectzoology
