309 



NOTE ON THE EPIPHRAGM OF ACEATINA IMMAGULATA, Lam. 



By Edgae a. Smith, F.Z.S., etc. 



Read Ufh April, 1899. 



Although mention has been made by Piscber^ and others that the 

 epiphragm in the genus Acliatina has a slit, instead of a round 

 perforation, as in Helix, during the first stage of formation, no 

 description of the peculiar ridge which is present on the inner side 



Fig. I. Aperture oi Achatina inimaculata, Lam., showing the epiphragm in situ. 

 ,, II. Inner view of the epiphragm when removed from the shell. 



appears to have been given. It may therefore be of interest to 

 describe this structure as met with in A. immaculata, Lam., from 

 Nyasaland. 



The form of the epiphragm is, of course, practically that of the 

 aperture of the shell, although it withdraws a little way back from 

 the extreme edge at the lower, or anterior, end. This is necessary in 

 order to allow a notch or sinus on the inner edge to fit under the 

 columella. The smooth surface is not quite level, this unevenness 

 resulting from the margin being modelled to the shell at varying 



1 Journ. de Conch., 1853, pp. 397-403. 



