™ 
402 HELICIGONA LAPICIDA. 
The CEPHALIC RETRACTOR arises very early from the great columellar muscle, 
the RIGHT TENTACULAR RETRACTOR having the earliest origin, and passing in its 
course between the male and female organs of the reproductive system to the 
right ommatophore ; the retractor muscle of the left ommatophore arises from that 
of the right side near the base, but in this species both retractors are devoted 
mainly to the retraction of the anterior part of the foot, each detaching a slender 
branch to serve the lower tentacle of their respective sides ; the broad strap-like 
BUCCAL RETRACTOR arises later, and on approaching the bneeal bulb is deeply 
cleft, each branch subdividing for attachment to the buecal mass. 
The ALIMENTARY SYSTEM is triodromous, and scarcely differs in its proportions 
from that of H. rufescens; the GSOPHAGUS is long and longitudinally striped, 
merging almost insensibly into the Crop, which is long and_ cylindrical, but 
expanding somewhat in the region of the true stomach, which terminates the 
Fic. 460.—Alimentary organs of Hediczgona lapicida, x 2, showing also the salivary glands, renal 
organ, and heart, and the method in which the cephalic branch of the aorta loops the gut. 
ingestive tract: the SALIVARY GLANDS are white and embrace the median portion 
of the cesophagus ; the DUCTS are slender and about 5 mill. long ; the DIGESTIVE 
GLAND is ochreous-yellow, and covered with brown blotches ; the KIDNEY may be 
buff, veined with brown, or cream coloured with reddish-brown marks or blotches. 
The JAW is about a millimetre in width from side to side, arcuate from front to 
back, and broadly crescentic in shape, being about 
half-a-millimetre from the upper to the cutting 
margin, and of adeep fawn colour, the ends abruptly 
cut off, and not rounded, with distinct but fine per- 
pendicular and more delicate horizontal strive; the 
vertical ribs are four or five in number, inconspicu- Fig: 461.— Jaw of. Vapronie x 20 
ous and flat and crenulate the upper and lower Castle Bolton, Yorkshire 
margins; there are also three or four darker lines (from photo. by Mr. W. Bagshaw). 
of different lengths representing thickenings, subparallel to the upper and lower 
margins and to each other. 
The RADULA is long and narrow, about 5 mill. in length and 14 mill. in width, 
and composed of about 250 transverse rows of teeth, each row constituted by about 
71 teeth, which include a well-developed unieuspid median tooth, hearing a very 
broad and strong mesocone, with no trace of accessory ectocones ; the laterals are 
about fifteen in number, the admedians being simply obliquely unicuspid, but the 
tenth to fifteenth teeth are really transitional in character, and show traces of an 
ectocone about the tenth tooth, which rapidly develops as the teeth recede further 
from the median line; an endocone also becomes faintly discernible, but becomes 
suddenly very powerfully developed on the sixteenth tooth, and initiates the mar- 
ginal series, which are usually about nineteen in number. 
2 e 
30 2 @ 
; 29 a 
ot 2 “ow 
Fic. 462.—Representative denticles from’ the radula of Helicigona lapicida, highly magnified 
(from a photograph by Mr. W. Bagshaw of a preparation by Mr. J. W. Neville). 
ev) The teeth as they{approach the outer edges of the membrane gradually decrease 
{ in size, and the endocone becomes almost equal in importance to the mesocone ; 
while the ectocone becomes gradually distinct and almost equal in size, but at the 
outer margins tends to become bifid. 
The formula of a Castle Bolton specimen, collected by Mr. W. Denison Roebuck 
and prepared by Mr. J. W. Neville, is 
ee t+h54+t4454+24% x 250 = 17,750 teeth. 
