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NATURAL SCIENCES OF PHILADELPHIA. 215 



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

 attachment and inner side cutting point. Marginals (b) low, 

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

 bearing one inner, broad, long, oblique, bifid cutting point, the 

 inner division the smaller, and two outer, smaller, stout, sharp, 

 side cutting points. 



Subgenus Aqlaja. 



Jaw thick, high, arched, ends but little attenuated, blunt ; cutting 

 edge without median projection ; anterior surface with stout, sepa- 

 rated ribs, denticulating either margin, from 5 to 9 

 in H. infumata (fig. 58), about 6 in fidelis. The 

 other American species, H. Hillebrandi, I have not 

 examined. 



Lingual membrane long and narrow. That of 

 Jaw of Hillebrandi not examined, those of infumata and 



Helix infumata. .... 



fidelis agreeing m their general characters. The 

 centrals have a base of attachment longer than wide, with incurved 

 lower margin and expanded lower lateral angles ; upper margin 

 broadly reflected ; reflection short, stout, with no side cusps or 

 cutting points, but a very stout, short median cusp, bearing a 

 short cutting point. Laterals like the centrals, but unsymmetri- 

 cal by the base of attachment wanting the inner, lower lateral 

 expansion ; it is, however, unusually developed on its inner side 

 margin : first marginals (b of each figure) differing from the late- 

 rals by the equalling of the reflection and base of attachment, the 

 lesser development of the cusp, and greater development of the 

 cutting point, which is bluntly bifid, the inner division the smaller. 

 On some of the first marginals of infumata (pi. XIIL, fig. 9, b) 

 there is a small side cutting point. Marginals low, wide, the re- 

 flection equalling the base of attachment, and bearing one long, 

 oblique, wide, bifid cutting point, the inner division the smaller, 

 and one or two short, sharp, side cutting points. There is great 

 variation in the cutting points. 



A comparison of the two figures will show a longer base of at- 

 tachment in fidelis, with a line of reenforcement or duplication to 

 its upper margin. As with all species, there is much variation in 

 the length of the cutting point, in centrals and laterals, and their 

 arrangement and development in the marginals. 



