30 MACfeODONTES. 



The lamellae and folds vary from very large in some species to 

 mere vestiges in others. 



The genus Macrodontes has hitherto been considered a subgenus of 

 Odontostomus, but it differs in the following characters : The shell 

 has fewer whorls, spirally lirate apex with no vertical striae, and a 

 marginal, tubercular parietal tooth in place of an entering lamella. 

 The genital system is far less elongate. The lung is short, densely 

 reticulate on the cardiac side, with strong secondary and tertiary pul- 

 monary veins developed. The secondary ureter is wholly open, but 

 slightly differentiated. The jaw is smooth. Finally, the central and 

 lateral teeth are unicuspid. These several differences clearly entitle 

 Macrodontes to generic distinction. In the soft anatomy, but not in 

 the shell, it approaches Anostoma. In the pattern of lung venation 

 it departs from the Bulimulida generally. 



Key to Species of Macrodontes. 



1. Aperture oblong, exceeding a third of the shell's length ; ground- 

 color brown. 



a. Basal keel long and curved, somewhat lateral ; plain or 

 banded ; teeth well developed. 



b. Aperture pink, its width contained 1^ times in its 



length ; uniform reddish-brown. odontostomus. 



b. 1 Aperture dark within, its length nearly double the 



width; the lip white or bluish, with two angles on 



the left side. 



c. Uniform cinnamon-brown ; length 35, diam. 



11 mill. gray anus. 



c. 1 With many whitish lines on a dark ground ; 



length 38-40 mill. fasciatus. 



rt. 1 Basal keel short, median and subvertical when viewed 



from the back, and but slightly arcuate ; plain or striped. 



b. Aperture narrow, nearly filled with large teeth ; 



length of shell fully 3 times its diam. paulistus. 



b* Aperture open, with the teeth very small or obsolete ; 



form obese. dautzenbergianus. 



2. Aperture squarish-ovate, about one-third the length of the shell ; 

 color yellowish-green ; basal keel short, teeth subobsolete. 



deyeneratus. 



