OF CONCHOLOGY. 



207 



blunt, scarcely attenuated ; with six prominent, sharp ribs, 

 equally visible on both anterior and posterior surface, their ends 

 strongly pectinating both margins, (See fig. 11.) 



Lingual membrane long and narrow, with numerous rows of 

 about 45 — 1 — 45 teeth each. Teeth as usual in the genus. (See 

 fig. 308 on p. 176 of Land & Fr. Water Shells of N. A., Part 

 I.) The bicuspid denticle on the uncini is still more developed 

 than in that figure. 



Helix fidelis, Gray, (Plate 9, fig. 1, 9.) 



Jaw short, broad, thick, rough, strongly arched, ends attenu- 

 ated, blunt, cutting edge with a well developed blunt median 

 projection, marked with decided longitudinal striae, which crenu- 

 late its margin. (See fig. 1.) 



Lingual membrane long and narrow, composed of numerous 

 rows of about 48 — 1 — 48 teeth each. Centrals long, expanded at 

 base, narrowed rapidly towards the apex, which is recurved and 

 prolonged into a short, stout, conically pointed denticle, without 

 decided lateral denticles. Laterals about 24 in number, much 

 resembling the centrals in shape, but with decided lateral ex- 

 pansions or denticles to the recurved apex, that nearer the 

 central line being the larger. Uncini about 24 in number, ir- 

 regularly denticulated, usually with one large bifid or tricuspid 

 denticle and two small denticles. The figure shows one central 

 and one lateral tooth. (See pi. 9, fig. 9.) 



Helix Hemphilli, Newcomb, (Plate 9, fig. 3.) 



Jaw thick, very much arched, of almost uniform breadth 

 throughout ;. striate transversely and vertically ; ends not atten- 

 uated, squarely truncated ; cutting edge with a blunt, prominent, 

 median projection. 



Lingual membrane with about 20 — 1 — 20 teeth in each row. 

 Centrals and laterals as usual in the genus. Uncini long, nar- 

 row, with one long blunt denticle and a second quite small one 

 at its side. 



Helix Cooperi, W. G. Binn. 



Jaw thick, slightly arched, ends attenuated, blunt ; cutting 

 edge with no median projection, but regularly crenulated by the 

 ends of numerous broad, subobsolete ribs : these slightly devel- 

 oped ribs extend but a short distance from the cutting edge. 



Helix stenotrema, Fer. 



Jaw long, rather broad, arched, ends not much attenuated, 

 squarely truncated ; anterior surface with eight stout ribs, den- 

 ticulating both margins. 



