178 PLEURODISCIDAE. 



case their divergence from the common stem of the other 

 groups must have been prior to the branching out of the 

 Achatinellidae, Tornatellinidae, Pupillidae, Valloniidae etc., 

 all of which had acquired similar penial complications before 

 the parting of their several ways. 



On the whole, the inclusion of Pleurodiscidae in Valloniidae 

 appears to be without satisfactory basis. That classification 

 was apparently prompted by a desire to restrict the number of 

 families. I see no advantage in claiming a relationship which 

 involves so many difficulties. 



1, Shell of moderate size, discoidal; penis very short, with 

 apical papilla through which the long, internally ridged 

 epiphallus enters; prostate gland long, about equal to the 

 uterus; spermathecal duct moderately long (Pleurodiscinae) 



Genus Pleurodiscus Wenz. 



2. Shell minute, depressed conic or turbinate ; penis abruptly 

 terminated ; prostate gland short, posterior ; spermathecal duct 

 short. (Pyramidulinae) Genus Pyramidula Fitz. 



Genus PLEURODISCUS Wenz. 



Pleurodiscus Wenz, 1919, Nachrbl. Deutsch. Malak. Ges. 

 vol. 51, p. 778, type Goniodiscus (Pleurodiscus) halmei (Pot. 

 et Mich.). 



Helix, Patula and Patulastra of some authors; not Patu- 

 lastra Pfeiffer as restricted to ^'Patula" pygmaea Drap. by 

 Kobelt, 1880, 111. Conchylienbuch p. 231. 



For anatomy see Hugh Watson, Proc. Malac. Soc. Lond. 

 vol. 14, p. 6. 



The shell is Discus-like, openly umbilicate, depressed, of 5y^ 

 to 6 whorls, the apical 2i/2 smooth, the rest costulate. Aper- 

 ture lunate; peristome sharp, somewhat dilated at the 

 columella. 



The jaw is thin, closely striate, the edges of the folds slightly 

 free (Man. Conch. IX, pi. 15, f. 2). Radula of P. lalmei with 

 17-9-1-9-17 teeth. Central tricuspid, smaller than the laterals, 

 which are bicuspid. Marginals wide, pectinate. 



Reproduction ovo-viviparous. Penis yevj short, the epi- 

 phallus entering through a short blunt papilla. Epiphallus 



