,/ 
420 WELICIGONA ARBUSTORUM. 
The GYPSOBELUM or dart varies in size in different individuals and varieties from 
three to five mill. in length, and is rarely absent from adult shells between the 
months of May and August, probably indicating it as more persistently retained 
than in some other species. 
a 
Fic. 474. Fic. 475. Fic. 476. 
Fic. 474.— Fully mature Gypsobelum or ‘‘ Love-dart” of Hedictgona arbustorum X 3. 
Fic. 475.—Section through the lenticular head x 7. 
Fic. 476.—Gypsobelum or ‘‘ Love-dart,” scarcely mature x 7. 
When fully mature, the dart has a beautifully curved and hollow shaft, 
expanding below into a funnel-shaped base of attachment, without any distinct 
traces of a basal annulus; towards the free-end the stem abruptly enlarges to 
form a substantial, compressly lanceolate head, which at full maturity occupies 
more than a third of the entire weapon, and is lenticular in transverse section, 
gradually tapering to a fine terminal point. 
Though in different individuals the darts are subject to a considerable amount 
of variation in size and relative proportions of parts, yet they are always calcareous 
and opaque, of a beautiful glistening white, and when immature are always slighter 
and more delicate throughout, the base less inflated, the head smaller, and its 
angles more acute and sharply pointed. 
The SPERMATOPHORE or capreolus is a firm and spirally twisted, flatly filiform 
body of a greenish-brown colour, with apparently overfolded edges, which becomes 
Fic. 477. Fic. 478. 
Fic. 477.—Imperfect Spermatophore of Hledicigona arbustorum, extracted from the diverticulum 
of the spermatheca (greatly enlarged). 
Fic. 478.—Spermatophore within the diverticulum, partially disintegrated (greatly enlarged). 
brittle and rigid by exposure to the air. It has three complete spiral coils, which 
probably terminate in a straight slender extension at each end, the whole forming 
a very perfect replica of the flagellum and adjacent part of the epiphallus within 
which it is moulded. 
The JAW or mandible is 0°75 mill. high and 2 mill. from side to side, strong 
and substantial, dark brown in colour, and rather flatly lunate in form, but varying 
considerably in the amount of curvature, with bluntly rounded or angulated ends, 
and very convex from front to rear. Though somewhat variable in number, there 
are usually five vertical or slightly divergent projecting ribs on the anterior face, 
which strongly denticulate both margins, but others less prominent may be inter- 
posed between the more developed ridges or may contribute to fill the area towards 
Fic. 479. Fic. 480. 
Fic. 479.—Mandible or jaw of Helicigona arbustorum x 8. Selby (from a micro-photograph 
by Mr. W. Bagshaw of a preparation by Prof. Gwatkin). 
Fic. 480.—Mandible or jaw of Helicigona arbustorum X 8. Beverley (from a preparation by 
Mr. J. D. Butterell). 
the outer extremities. In the Selby specimen figured, there is a pair of slightly 
divaricated and strongly developed submedian ribs enclosing between them a well 
developed though narrower central one, while two other less prominent ribs oceupy 
the outer area; these teeth all strongly denticulate the lower or cutting margin, 
while the smooth outline of the upper margin is only slightly influenced in contour 
by the two subcentral ridges. 
The minute sculpture is composed of horizontal wavy incremental lines, and 
there are also vertical or perpendicular lines of striation, 
