NATURAL SCIENCES OF PHILADELPHIA. 219 



H. Dupetithouarsi, not examined. 



H. ruficincta (pi. XIV., fig. 3), 35 1 35, with 18 laterals. 

 H. Gabbi, not examined. 



H. facta (see p. 216, fig. 60), 29129, with 11 laterals. 

 H. Kelletti (pi. XIII., fig. 4), 57 1 5Y- 



H. Stearnsiana (pi. XIII., fig. 3), 50 1 50, with 24 laterals. 

 The 22d tooth has the side cutting point. 



Subgenus Glyptostoma. 1 



One species only is thus far known, Helix Neivberryana. Its 

 jaw (pi. XVI., fig. 4) is low, wide, slightly arcuate, ends but little 

 attenuated, blunt ; cutting margin without median projection ; 

 anterior surface with numerous (about 16), stout, separated ribs, 

 deeply denticulating either margin. 



Lingual membrane (pi. XIII., fig. 6) long and narrow. Teeth 

 41 1 47, with 17 perfect laterals. Centrals with the base of 

 attachment long and narrow, with greatly expanded lower, lateral 

 angles, the upper margiu rounded, broadly reflected ; reflection 

 large, stout, with obsolete side cusps, but with decided, triangular 

 side cutting points ; median cusp very stout, short, with a long 

 acute cutting point reaching beyond the lower edge of the base of 

 attachment. Laterals like the centrals, but unsymmetrical by the 

 suppression of inner, lower, lateral angle of the base of attach- 

 ment and inner side cutting point. The transition from laterals to 

 marginals is marked by the lesser proportional development of the 

 cusp and greater development of the cutting point. Marginals (c) 

 low, wide, the reflection equalling the base of attachment and 

 bearing one inner, short, stout, oblique, blunt cutting point, and 

 one outer, shorter, blunt cutting point. 



This species, like all others, has great variation in the develop- 

 ment of the cutting points on different parts of the same membrane. 



Subgenus Euparypha. 



Jaw high, arcuate, ends but little attenuated, blunt ; cutting 

 margin without median projection; anterior surface with a few 

 (about 5 in Tryoni) stout, separated, unequal ribs, deeply denticu 

 lating either margin. 



1 See Proc. Phila. Ac. Nat. Sci., 1873, p. 244. 



