52 University of Michigan 



acters, Giippya cJiampioni von Martens, G. hrowni Pilsbry, and 

 G. costaricana Pilsbr}', with the variety elatior Pilsbry, appear 

 to belong in this group. All of these species are large shells 

 with weak spiral and radial striation and rather rapidly 

 increasing whorls. 



On the basis of the radula alone, Euconulus would certainly 

 become a subgenus of Habroconus, and the latter would be 

 separated genericly from Guppya. However, Crosse and 

 Fischer (1872) remark: "After M. Bland (in letter), it fol- 

 lows from a verbal communication made to him by Dr. 

 Berendt, who had occasion to examine in living state Helix 

 selenkai, that that mollusc possesses, at the posterior extremity, 

 a mucous pore quite (tout a fait) close to that of Stenopus" 

 (translation). This appears to indicate a closer affinity with 

 Guppya, although Euconulus also has a mucous pore. 



In addition, Euconulus is a Holarctic genus, and in general 

 the American forms decrease in size towards the south. (From 

 the shell characters, I think it probable that G. micans Pilsbry 

 and G. Jalisco Pilsbry also will be found to belong in Euconu- 

 lus.) Guppya, on the other hand, is a neotropical genus, whose 

 forms (for example, G. vacans, G. gnndlachi and G. sterkii) 

 tend to decrease in size toward the north — that is, in the oppo- 

 site direction. This appears to indicate a northern center of 

 origin for Euconulus and a southern one for Guppya. Habro- 

 conus only has, as far as known, neotropical species, which 

 are larger than any of the American forms of Euconulus. 



For these reasons, Habroconus is tentatively used here as a 

 subgenus of Guppya, while the more familiar Euconulus is 

 retained as a genus to include the conical forms with better 

 developed radial striations, and with all of the well-developed 

 marginals bicuspid. From the shell-characters, I rather doubt 

 if the acutely carinate species with practically no spiral stria- 



