NATURAL SCIENCES OF PHILADELPHIA. 221 
angle of the base of attachment; outer laterals with a more 
developed cutting point and a decided side cusp and cutting point; 
the change from the laterals to the marginals is shown in the 16th 
tooth (see fig. 63), where the base of attachment is wider, the 
reflection stouter and the inner cutting point becomes bifid. The 
marginals are low, wide, the reflection equalling the base of 
attachment, the inner cutting point short, bluntly bifid, the outer 
shorter and blunt. 
Fig. 638. 
“Ol GS GhT LOCLTE 
bod ha ‘lls 
Lingual dentition of Helix hortensis. [Morse.] 
Having no specimen to examine myself, I am dependent on 
Morse’s figures given above. 
Subgenus PoMATIA. 
Jaw of our only species, H. aspersa, introduced by commerce 
at Charleston, S. C. (where it is still common), high, thick, arcuate, 
ends but little attenuated, blunt; cutting margin without median 
projection ; anterior surface with 6 stout, separated ribs, deeply 
denticulating either margin (pl. XVI., fig. 8). 
Lingual membrane of the same species (pl. XIII., fig. 7, a, b, c) 
long and narrow. Teeth 50—1—50, with 15 perfect laterals. 
Centrals with base of attachment longer than wide, the lower 
lateral angles but slightly produced, the lower margin in some 
cases with a quadrate excavation or thinning as usually found in 
Succinea; the upper margin broadly reflected, reflection very 
large, with a very stout, short median cusp, bearing a short, stout 
cutting point reaching the lower edge of the base of attachment ; 
side cusps obsolete, but bearing well developed, short side cutting 
points. Laterals like centrals, but unsymmetrical by the sup- 
pression of the inner, lower, lateral angle of the base of attach- 
‘ment, and the inner side cutting point. ‘Transition teeth from 
the laterals to the marginals (b) with a more developed reflection, 
a shorter inner cusp bearing a greatly developed bifid cutting 
point. Marginals (c) low, wide, the reflection equalling the base 
