ASHFORD : ON THE DARTS OF BRITISH HELICID.E. 131 



5. Helix caperata Montagu, pi. v. figs. 6 — 8. Dart-sac 



attached to the vagina more than half its length, free 

 end ovate, somewhat pointed ; yellowish white, semi- 

 transparent, minutely spotted. Dart curved, slender, 

 sometimes slightly twisted ; base scarcely larger than 

 the middle of the shaft ; without blades or annulus. 

 Length 2| to 3^ mm. 



The dart-sac of this species appears small in consequence 

 of its fusion with the vaginal tube (figs. 6 & 7). It is associated 

 with two bundles of short mucous glands, normally eight in 

 number, usually simple, occasionally bifid, or even trifid. 



The elegant little dart (fig. 8) is of the simplest form. It 

 somewhat resembles a single dart of H. ericetorum^ but is 

 smaller, more slender, more gracefully curved, and less abruptly 

 pointed. In some cases the head is inconspicuously com- 

 pressed, in others the shaft enlarged very gradually from point 

 to base, but in no case does the diameter of the lower portion 

 much exceed that of the middle part. The solid part of the 

 base is thin, and often wrinkled, as if composed of an admix- 

 ture of more plastic animal matter with the mineral ingredient. 

 This condition is not however confined to the present species. 

 The transverse markings of the shaft are similar to those of the 

 last two species, though less pronounced, and I am inclined to 

 think they are, in some cases, merely optical effects due to in- 

 equalities in the degree of opacity, since the lateral lines of con- 

 tour do not always exhibit corresponding irregularities. 



Immature darts are less curved than mature ones. I have 

 found the sac equipped in November, January, and February, 

 as well as in the summer months. Of fully grown shells 95-96 

 per cent have furnished me darts. 



The figures are from specimens collected at Christchurch, 

 Hants. 



6. Helix Pisana Miiller, pi. v., figs. 9 — 16. Dart-sac 



short, stout, acorn-shaped ; pearly white. Dart 

 with a short straight shaft expanding rather abruptly 

 into an infundibuliform base ; provided with four 

 channel-edged blades; annulus of 12 to 16 rods. 

 Length 2\ mm. 



