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JOURNAL OF CONCHOLOGY, VOL. I4, NO. §, OCTOBftR, 1914. 



in the two halves of the same radula. It is apparent, therefore, that 

 in specimens of helvetica of approximately the same size the third 

 lateral tooth may be of various forms from an almost marginal to a 

 complete lateral type ; the drawings were all made from specimens 

 between 7*3 and 7*7 mm. diam. in the present series. 



Table II. 



The 23 specimens of the 8'o to 8'8 mm. series need not be dealt 

 with at such length. The data are given in Table 11. and show about 

 the same range of variation as the longer series. 



Conclusions. — The magnitude of spontaueous variation in the 

 number of rows and number of teeth in a row in Hy. helvetica is of the 

 same order as that of a linear dimension of a snail shell. The length 

 and breadth of the radula are apparently more variable. There is 

 also much variation in the configuration of the third lateral tooth. It 

 is clearly necessary to examine radulae from a series of specimens as 

 well as from specimens of known size. 



Jaminia cylindracea DaC. with two denticles. — While collecting this 

 species among the heather which covers an outcrop of tertiary strata on Ridgeway 

 Hill, Dorset, I took a specimen with a second denticle close beside the normal tooth. 

 This does not seem to have been noticed in_/. cylindracea though two and three 

 toothed forms oi J. muscomm are known. I should suggest that the name var. 

 iJ;^/a«a/'a be adopted. — ^J. E. A. JOLLIFFE {Read before the Society^ May 13th, 1914).' 



