HELIX HORTENSIS. 329 
The buccal armature of British specimens of this species as here described and 
figured show such striking differences to American and continental individuals as 
to merit serious investigation ; not only is the jaw different and the total number 
of teeth on the radula remarkably dissimilar, but the changes in the character of 
the teeth take place at different positions on the membrane. 
The JAW is about two millimetres broad from side to side, and somewhat arcuate 
from front to back, flatly and widely crescentic in shape, and of a deep fawn colour, 
with thinner and bluntly-rounded ends, and perceptible strize and growth lines. The 
transverse ribs are vertical but slightly divergent, and are very prominent, re 
cially on the anterior face; they are usually three or more in number, medially 
placed, and strongly denticulating both the upper and cutting margins. 
1 
Fic. 383. Fic. 384. Fic. 385. 
Fic. 383.—Jaw or mandible of an adult Helix hortensis from Beverley (from a preparation by 
Mr. J. Darker Butterell), x 12. 
Fic. 384.—Jaw or mandible of an adult A. hortensis from Maine, U.S.A., much enlarged 
(after Prof. E. S. Morse). 
Fic. 385.—Jaw or mandible of AY. Aortenszs, much enlarged (after Moquin-Tandon). 
Moquin-Tandon describes the transverse ribs on the jaw of this species as six in 
number, although his figure indicates seven, as denticulating the cutting margin, 
but both figure and description are scarcely representative, as six is an excessively 
rare number of ribs and seven almost unknown ; three more or less distinct ribs 
is the average number possessed by the species and the usual number present in 
British specimens. 
In 1864 Prof. Morse described and figured the jaw of an adult specimen from 
Maine, U.S., as possessing upon its anterior surface five stout and well developed 
vertical ribs, of which the median one is the most prominent; they strongly denti- 
culate both margins, and are restricted to the central portion of the organ. 
The RADULA is oblong in shape and about six mill. in length and two mill. 
in width, and composed of one hundred and fifty or more transverse rows of teeth, 
each row constituted by ninety-five teeth and composed of an unicuspid and powerful 
oo 
gr’ 
no ae 
2G gm 
Fic. 386.—Representative denticles from the radula of /fe/7x hortensis, highly magnified (from 
a preparation by Rev. Prof. H. M. Gwatkin). 
central tooth, Hanked by a series of about sixteen laterals ; the admedian teeth are 
unicuspid, similar to the median tooth, but gradually becoming more asymmetrical as 
the teeth recede from the centre, an ectocone becoming perceptible at the thirteenth 
tooth, and showing a transitional character; the marginals are about thirty in 
number, and tricuspid in plan, due to the bifurcation of the mesocone, which 
commences at the seventeenth tooth; towards the margins they, however, occasion- 
ally become quadricuspidate by the splitting of the ectoconie points also. 
The formula of a Paignton specimen prepared by Rev. Prof. H. M. Gwatkin is 
3 TCM Ro a) Aes a Fy Or 
FP416434164 31 x 150 = 14,250 teeth. 
Dr. W. G. Binney in 1878 described and figured the radula of an American specimen 
in which a decisive bifurcation of the mesocone is shown on the eleventh tooth, and 
the presence of an ectocone is indicated even on the first admedian tooth, and is 
shown powerful and well developed on the sixth lateral, while the representation of 
the twenty-sixth denticle is distinetly pentacuspidate. 
