297 



THE RADULA OF HYALINIA. 

 III. 



The Radular Characteristics of Hyalinia helvetica from different localities. 



By a. E. boycott. 



(Read before the Society, October 14th, 1914). 



In this paper I propose to describe shortly the results of the examina- 

 tion of the radula of Hyalinia helvetica from four different English 

 localities. The specimens were all collected by myself in 1911-1913 

 at (i) Banstead in Surrey, (2) English Bicknor in West Gloucestershire, 

 (3) Tremadoc in Carnarvonshire, and (4) Marple in Cheshire. All 

 the radulis were prepared and examined in the same way — a point 

 which may turn out to be of some importance. The mean results of 

 enumeration and measurement are given in the following tables, the 

 specimens being classified into size groups in accordance with the 

 conclusions previously reached {th\5 Journal, vol. xiv. (19 14), p. 214). 



Table I. 



Table II. gives the averages of these mean figures for the 7 and 8 

 mm. groups, there being no representatives of the 9 mm. group in the 

 Banstead series. 



Table II. 



