JOURNAL OF CONCHOLOGY. 1 95 



THE DARTS OF BRITISH HELICID^. 



By CHARLES ASHFORD. 



PART V. 



10. Helix arbustorum L., pi. viii., figs, i — 4. Dart-sac 



clavate or cylindrically clavate ; usually bluish-grey or 



livid, but variable in colour ; outer surface minutely 



spotted, inner coat dark brown. Dart curved, central 



part of shaft narrow and nearly cylindrical ; base 



gradually but boldly expanded ; head lanceolate, long, 



thick, broadly-flattened, blunt-edged, polished, opaque; 



annulus absent. Length 4 to 5 mm. 



As in the case of other coloured dart-sacs already described 



that of H. arbustorum is white during the early period of growth 



and acquires its colouring matter in the later stages of maturation. 



Its outer coat is grey and obscurely transparent, the inner one 



brown, modified with red, purple, or violet. The free end of the 



sac sometimes appears a shade darker than the rest — as is the 



case also with that of H. neinoralis — owing to the greater width 



of the dark inner sheath in that locality. The sac has no second 



lobe and is not fused to the vagina. 



The dart-sac lies between two long, simple, stout, subulate 

 mucous glands which vary from 15 to 25 mm. in length. They 

 are tough, as thick as the dart-sac itself, and taper to a blunt 

 point (fig. i). One extremity is occasionally bifid (fig. 2). In 

 colour the glands are grey, tinged \vith some shade of lavender, 

 dirty-green, dull-blue, ochre, or even russet-orange, sprinkled 

 with minute spots or .fine streaks, and it is not uncommon for the 

 dart-sac to share with them the same tint. The reader will re- 

 call the simple club-shaped mucous glands of H. Pisana. Those 

 of the present species are never like them thickest near the 

 extremity. Particularly interesting is the occasional occurrence 

 of a terminal fissure represented of natural size in fig. 2, as 

 showing the first step towards the highly ramose development 

 acquired by H. aspersa, and still more strikingly by H. pomatia. 



