1 68 ASHFORD : ON THE DARTS OF BRITISH HELICIDiE. 



Adolf Schmidt in 1849 first drew attention to the difference 

 between the darts of this and the last species, and a more de- 

 tailed description than here given will be found in the ' Mai. 

 BUitt.' for that and the succeeding year. In some additional 

 remarks in the same journal for 1853, he says : " The darts are 

 so different that an ambiguous form between the two is incon- 

 ceivable (undenkbar). I have dissected hundreds of both kinds 

 and have thereby arrived at the full conviction that in their 

 darts lies the specific difference which must determine each 

 individual case in question." 



To this may be added that the darts of H. hortensu, inter 

 se, are remarkably uniform in character. They may be com- 

 pared to plates in a dinner-service, differing in size and some 

 minor particulars, but impossible to be confounded with those 

 of another pattern. Doubtful cases then are to be determined 

 by their darts. But what if the dart be not forthcoming ? We 

 must fall back upon the mucous glands. And, variable as these 

 organs confessedly are, we may in some cases arrive at a reliable 

 decision, if we regard their total aspect — the resultant, so to say, 

 of their length, mode of ramification, number of branches, form, 

 colour, and texture. 



I received through the kindness of Mr. W. Jeffery of Chi- 

 chester, a batch of very suspicious looking shells — large, yellow, 

 bandless, dark-mouthed, with coloured inner lip. The darts 

 proved them to be a variety of H. horfensis, and the mucous 

 glands were in accord. 



Shells with various shades of lip are rather common round 

 Christchurch, and I have carefully examined about 150. Many 

 of them could scarcely be called doubtful, even at first sight. 

 Moreover they were taken from the iiortcnsis colony where H. 

 nemoralis in its typical form does not occur. I was not sur- 

 prised therefore to find every case — where the test of dart-form 

 was available — referable to the present species. The following 

 tabular statement, arrived at from an average of fifty members of 

 each kind, shows how far the mucous glands of the variety just 



I.e., iv., April, 1S84. 



