ASHFORD : ON THE DARTS OF BRITISH HELICID^. IO9 



The dart-sac of Z. nitidus differs from that of any British 

 HeUx by its recurved extremity (fig. i) and by the presence of a 

 slender filament (muscle?) attached to the terminal part of the 

 sac. The retractor muscle of the penis-sheath joins that of the 

 dart-sac and the common part above is attached to the sperma- 

 theca-duct. This arrangement bears a striking resemblance to 

 that described and figured by Leidy (in Binney's " Terrestrial 

 Air-breathing Mollusks of the United States" 1 851) as existing 

 in the transatlantic forms Helix intertexta and H. suppressa. 

 In the earlier stages of growth of the dart-sac the pendent lobe 

 is not always observable but the connecting filament appears to 

 be always present. 



It is with some hesitation I give fig. 2 as representing the 

 fully formed dart in British specimens not having had the 

 opportunity of comparing a series. Out of about one hundred 

 individuals obtained from Yorkshire and Hampshire in July and 

 August only one had a dart. The rest, with few exceptions, had 

 the sac in a very early stage of development though the shells in 

 most cases were apparently mature. Lehmann describes the 

 dart of German specimens of Z. nitidus as having the base 

 funnel-shaped and the head slightly lancet-shaped. I have no 

 reason to suppose that British specimens are otherwise, when 

 matured, and therefore think it highly probable the form repre- 

 sented in fig. 2 is that of a dart not fully completed. 



The figures are drawn from specimens kindly sent me from 

 Beverley by Mr. Darker Butterell of that place. 



2. Zonites excavatus Bean, pi. iii., figs, 5 — 10. Dart- 

 sac long, slender, with a bi-lobed, pendent free end ; 

 pearly white, nearly transparent. Dart with a fili- 

 form, curved, twisted shaft, slightly flattened and 

 widened towards the point ; base rather abruptly 

 expanded ; without blades or annulus ; length 2 to 

 2'5 mm. 



Till the present year the last species has been considered 

 to afford the only instance of a European Zonites furnished with 



