North American Terrestrial Mollusks. 167 



We have not noticed in any of the Helicidm the vertical 

 median carina to the jaw, often present in the VitrinincE. 



Patula (p. 71). — We propose to recognize this as a 

 genns, following the more recent decision of von Martens 

 (Preuss. Exp. p. 258). It will take precedence of the 

 genus Helix. To the description of the shell and animal 

 alread}^ given, we may add that in the American species the 

 jaw cannot be said to be ribbed, as usual in Helix. On that 

 of several species, however, there are subobsolete ribs or 

 wrinkles near the cutting edge, which they sometimes crenel- 

 late. The prevailing type of jaw seems to be such as we 

 have tigured for P. alternata (p. 75). 



Lingual membrane as figured on p. 75. The marginals, 

 however, are serrate in P. af^teriscus. In the other species 

 they have oue long, inner, oblique, blunt denticle, and one 

 or more short, side denticles. 



For the description of the jaw and lingual membrane of 

 the genus Helix (p. 69) may be substituted the descriptions 

 given by us al)ove for the jaw and lingual membrane of the 

 subfamily Helicinoe. We have noticed in the genus Helix, 

 as now constituted, every form of jaw which we have de- 

 scribed at length above, except that having angular lipper 

 median plates. 



With the exception of Patula, we still retain the genus 

 Helix in the sense in which it is used by Albers and von 

 Martens. With all those who have studied the genus, we 

 are aware that it contains numerous natural groups, many of 

 which appear to be sufficiently well marked to warrant their 

 being recognized as distinct genera; space, however, does 

 not permit of our considering this part of the subject. 



Genus Bulimulus (p. 191). — To the description of the 

 jaw must be added, "often presenting the appearance of 

 separate plates, sometimes arranged obliquely towards the 

 central line, so as to form an upper triangular plate, as in 

 Cylindrella.'''' This last form is usualjy thin and almost 

 transparent. 



