Dentition of Pulmonate Mollusks. \'l\ 



Jaw arched, high, ends attenuated, blunt; an obtuse median projection to 

 cut ling edge; transverse lines of reinforcement, but no ribs. 



An unusual form of jaw in this genus, though common in many sub- 

 genera of Helix. 



Drymmis Lobbi, Rve. Between Balsas and Cajamarca, Peru. 

 Prof. Orton. 



Jaw (PI. XY, fig. P) thin, transparent, as usual in the genus, with 21 

 narrow, distant ribs, serrating either margin, running obliquely towards 

 the centre of the jaw, so that those of the upper centre meet or end before 

 reaching the lower margin ; the substance of the jaw is so thin that it di- 

 vides, on maceration, into separate pieces at the ribs; in some specimens 

 the jaw seemed to be formed of distinct plates, whose overlapping forms 

 the ribs; I have no doubt, however, that it consists of one single piece. 



Lingual membrane (PI. XIV, fig, E) broad, very delicate in texture, and 

 difficult to handle ; numerous rows of 90-1-90 teeth; the centrals have the 

 base of attachment longer than wide, with lower lateral expanded angles ; 

 the reflection has one stout, median cusp, the side cusps being obsolete; this 

 cusp bears a short, rapidly attenuated, sharp cutting point ; the laterals are 

 of same type as centrals, but differ widely in the cutting point, which is 

 oblique, extremely long, broad as the upper margin of the base of attach- 

 ment, bluntly rounded at its end, near which on the inner side is a promi- 

 nent, blunt notch; the marginals are low, wide, with a very oblique cusp, 

 bearing a much broader, trifid cutting point, the middle one much the 

 largest, all with curving sides. 



DrymcBus Bahamensis, Pfr. New Providence, Bahamas. 

 Gov. Rawson. 



Jaw as usual in the genus, over fifty ribs ; in some specimens the ribs at 

 the centre meet or end before reaching the lower margin, so oblique are they; 

 in others they are so slightly oblique as to reach and serrate the lower 

 margin. 



Lingual membrane (pi. XII, fig. F) with no lateral teeth, all the side teeth 

 being marginals of the form described in B. Lobbi. 



DrymcBus Rawsonis, H. Ad. Tobago. Gov. Rawson. 

 Lingual membrane as in last species. 



Liostracus multifasciatus, Lam. Antigua. Gov. Rawson. 



Jaw as usual in the genus. 



Lingual membrane as in last species ; the cusp of the central tooth has 

 three cutting points. The marginals are in waving rows. 



