THE CYCIjOPHO'RiID LAND MOLLUSKS OF AMEtRICiA 83 



back of the neck behind the tentacles. It is swollen basally and pro- 

 vided with a seminal groove and a very short simple terminal 

 appendage. 



KEY TO THE SPECIES OF THE GENUS PTYCHOCOCHLIS * 



Nodulations present on base. 

 Nodulations on base strong. 



Strong nodulations of base extending from umbilical keel to 

 periphery. 



Strong nodulations present on base of all of last whorl. 



Upper side of last whorl very coarsely wrinkled corrugatior 



Upper side of last whorl not very coarsely wrinkled. 



Wrinkles of base coarse gossei 



Wrinkles of base fine. 



Shell more than 20 mm. in diameter varians 



Shell less than 14 mm. in diameter gemma 



Strong nodulations present on base of early portion of 

 last whorl only. 

 Nodulations strong on all the upper surface of last 

 whorl. 



Umbilical keel strong welchi 



Umbilical keel obsolete manchesterensis 



Nodulations not strong on all the upper surface of 

 last whorl but obsolete on last part. 



Nodulose ridges retractively slanting at periphery, taylori 

 Nodulose ridges protractively slanting at pe- 

 riphery. 



Nodulations coarse zigzag 



Nodulations finer shawae 



Strong nodulations of base not extending from umbilical 

 keel to periphery. 



Nodulations of upper surface of last whorl few and 



distantly spaced clappi 



Nodulations of upper surface of last whorl not few or 

 distantly spaced. 



Shell gigantic, greater diameter more than 32 mm senex 



Shell not gigantic, greater diameter 27 mm. or less. 



Nodulations on base very strong corrugata 



Nodulations on base not very strong adanasi 



Nodulations on base feeble. 



Oblique, protractively curved wrinkles present near umbili- 

 cal keel simpsonl 



Oblique, protractively curved wrinkles absent near umbili- 

 cal keel. 



Weak nodules present on upper surface of all of last 

 whorl. 



Nodules on base weak martensi 



Nodules on base obsolete. 



Umbilicus wide hendersoni 



Umbilicus narrow marianna 



* I have not included P. suirugosa (Sowerby) in this key, since I have not seen specimens 

 of it. 



