400 PROCEEDINGS OF THE ACADEMY OF [1892. 



ably be found to intergrade with Chloritis in characters when more 

 species are known anatomically. 



Group V, HAPLOGONA. 



Genitalia entirely lacking accessory organs ; penis without an 

 epiphallus; jaw smooth (oxygnath), vertically striated (aulaco- 

 gnath), or flatly plaited (stegognath). Outer lateral teeth generally 

 multicuspid. This group may be classified thus : 



. , , ^ f A mucous pore on the tail -' Endodonta. 



Aulacognath or stegog- i ^ \ Patida 



nath; shell with sini- -{ No mucous pore ; aulac- , , " , 

 111- I .1 { Ano(;lvpta. 



pie, sharp lip. ^ ognalhous. \ Irochomorpha. 



Odontognath ; shell hav- f Polygyra 

 ing reflexed or thick- \ Polygyrella. 

 ened lip. (. ? Praticolella. 



Genus POLYGYRA (Say) Pilsbry. 



Proc. Acad N. S. Phila. 1889, p. 193. 



Anckistoma, in part, of H. & A. Adams, Tryon, Fischer, ei al. 



The genital system lacks all accessory organs, there being no 

 dart-sack, no mucous glands, no flagellum on penis; the duct of the 

 spermatheca is short and simple, without an accessory blind sack. 



The jaw is strongly ribbed, and there is no median projection on 

 its cutting edge. 



Oviparous, the eggs small, numerous. 



Shell helicoid, varying from globose to lens-shaped or planor- 

 boid ; horn-colored or brown, sometimes banded, the most constant 

 band supra-peripheral ; striated; lip flatly reflected ; aperture teeth 

 often wanting, but typically three— 1 parietal, 2 upon the lip ; 

 axis perforated, umbilicus open or closed. 



Distribution, North America. We have every reason to believe 

 that this group has been in the past, as it now is, exclusively North 

 American.^*^ 



Subdivisions. — The group is quite homogeneous, easy transitions 

 being traceable between the various sections, through species which 

 are quite intermediate. Sections: Polygyra s. str., Dcedalochila, 

 Triodopsis, Mesodon, Stenotrema. 



In the " Nomencl. and Check-list of Amer. Land Shells" (1888) 

 this genus was correctly defined, but several groups not agreeing 

 with my diagnosis were included. These groups were subsequently 



^®See Pilsbry, Journal de Conchyliologie, Paris, 1891, p. 22. 



