LITTORINA. 299 
234, Lirrortna DorsErensis, sp. nov., or ? var. of Litt. edilis. Plate XXIV, fig. 
3 (A), fig. 4 (B), fig. 5 (C). 
Cf. for B Trocuus eranarius, Héb. and Desl. Foss. Montreuil-Bellay, p. 53, 
pl. ii, fig. 8. 
Description, A and B: 
Length . ; : : . 14—17 mm. 
Length of body-whorl to total height . . say 50: 100. 
Spiral angle (convex) : ; S Gs 
Shell irregularly conical, spiral angle usually convex. Whorls seven, narrow, 
flattish, or slightly biangulated; suture well marked, rarely gaping. Within 
certain limits there is considerable variety, some shells being more trochiform, 
. others more turbinate. Apex sub-obtuse, the two apical whorls being smooth and 
full; in the rest of the spire and body-whorl there are three nodose spirals, the 
nodes being rather wide apart, decussated by short, thick, axial ribs. The base 
is rather flattened, with five or six plain spirals. Fine axial striw throughout. 
Occasionally a fourth spiral is developed (fig. 4), in which case we seem to 
have the most characteristic features of Trochus granarius, Héb, and Desl. 
Aperture sub-orbicular, with an extremely short and straight pillar lip, which is 
rounded off at the anterior extremity instead of being produced. 
Variety C.—Shell thin, eucycloid ; whorls biangulated, sutures rather gaping ; 
spiral ornamentation much subdued, axial striz conspicuous and very oblique. 
Pillar-lip rather longer than in vars. A and B, and the aperture less restricted 
in front. 
In a large series of specimens every gradation between A, B, and C may be 
noted. There are also specimens which approach “ Turbo” centurio (Goldf., 
pl. exciv, fig. 7). 
Relations and Distribution—The group of shells which I have focussed under 
Intt. Dorsetensis is primarily related to Litt. edilis. As a group given to sporting 
it helps to show how “ Littorina” and Amberleya seem to wait upon each other, 
even to the thinning out of the shell-substance when the eucycloid character is 
assumed. 
Extremely abundant in the concavus-zone at Bradford Abbas. A few very 
small specimens in the Pea-grit at Leckhampton. 
