BOYCOTT : SEXUAL DIFFERENCES IN CYCLOSTOMA ELEGANS. 325 



random and certainly with no conscious selection, for dissection : i6 

 proved to be females. If in the field the sexes had been separate and 

 the same unconscious preference for quite the largest specimens had 

 been exercised, I should have arrived at the startling result that 

 female Cydostoma were eight times as numerous as male individuals. 

 The present data do not of course afford any evidence to the contrary; 

 single females might all have been underground. It would be 

 interesting to determine the point accurately. In this series there was 

 no sexual difference in colour : 6 males and 7 females were of the pale 

 unmarked form. 



After drying to constant weight at Qo^C, the shells were weighed. 

 The males averaged o'i23 gms., the females o'i72 gms., a ratio of 

 100: 119. This is in almost precise relation to the calculated 

 volume. Assuming that the shell is a regular cone with a base equal 

 to half the sum of the two diameters, the males have an average 

 volume of 258 mm.^, the females 314 mm.', a ratio of 100: 122. 

 There is therefore no evidence that there is any sexual difference in 

 shell thickness. 



Some preliminary observations were made on the radula;. Ten 

 male radulse taken at random varied in length from 5*2 to 7*2 mm., 

 and the number of rows from 94 to 119 ; the averages were 5*99 mm. 

 and 107 rows. In the same way ten females gave a length of 6'64 

 (6 "4 to 7-4) mm. with 109 (102 to 126) rows. The male to female 

 ratio is therefore for length 100: in and for number of rows 100: 

 102, The female radula appears from this to be relatively small and 

 the teeth possibly relatively large or widely spaced. I have some 

 evidence in the case of Tachea that the size of radula and number and 

 size of teeth is proportional to the diameter rather than the calculated 

 volume of the shell, and the same may hold in Cydostoma. 



Conclusions. 

 I. — Female Cydostoma are definitely larger than male Cydostoma. 

 2. — No evidence was obtained that there is any sexual difference in 

 the tumidity of the shells. 



Carychium minimum var. elongatum nov. from Chatburn.— In looking 

 over my specimens of this interesting little shell, which I have taken in various 

 localities and counties, I find that those obtained at Chatburn are of a beautiful 

 slender elongated form, difiering considerably from specimens exhilnted from other 

 districts, with the exception of those from Long Preston, a village wide of Ilellifield, 

 which is also near the same branch of the Lancashire and Yorkshire Railway as 

 Chatburn. This form I propose to call var. ehugatum.—]. W. Baldwin {Read 

 befon the Society, May 12th, 1909). 



