112 ASHFORD : ON THE DARTS OF BRITISH HELICIDiE. 



mature examples the blades do not extend more than a third or 

 a quarter of the length, and at a still earlier stage no blades are 

 visible (fig. i6). The shaft is usually marked transversely with 

 coarse, irregular bands or ridges, resembling lines of growth, at 

 unequal distances from each other and varying in depth of 

 whiteness (fig. 17). I have found no annulus. The base is 

 the widest part of the shaft but there is no abrupt expansion. 



The inner sheath of the sac tapers to a point, rendering it 

 very diflScult to extract the dart by dissection. In using a solu- 

 tion of caustic potash to dissolve the integuments care must be 

 taken to wash the dart well, when free, otherwise the trans- 

 parency of the blades will be impaired by the formation of 

 minute white crystals upon their surface as the solution dries. 



Schmidt (Stylomm. pi. vi., fig 40) represents the dart-sac of 

 a variety of H. variabilis from Burriana with the free end deeply 

 bi-lobed and the whole sac of a slenderer shape. No such form 

 has occurred to me among British specimens, though an incip- 

 ient notch may occasionally be met with (fig. 12) showing a 

 tendency to'such a form as Schmidt illustrates. 



I have examined a considerable number of H. virgaia from 

 various localities including the var. suhmaritima from the Isle 

 of Wight and a small form kindly supplied by Mr. Ponsonby 

 from near Yeovil, Somersetshire, but have met with no departure 

 from the type of dart. The size varies much but is always in 

 proportion to the bulk of the animal. 



In the months of July, August, and September about 95 

 per cent of individuals with completed shells have furnished 

 darts. 



Neritina fluviatilis var. cerina Colb. in Hampshire. 



— Through the courtesy of my esteemed correspondent Mr. C. 

 Ashford, of Christchurch, I am enabled to add South Hants, to 

 the locality previously recorded for this pretty variety. Mr. 

 Ashford has kindly sent me a small specimen found by himself 

 in the river Stour near Christchurch in September, 1881. — 

 J. W. Taylor, Sep. 6th, 1883. 



I.e., iv., Oct., 1SS3. 



