Littorina arcana

Hannaford-Ellis, 1978

Description (shell):
Shell essentially like that of Littorina saxatilis , but spire smaller, eversion of aperture at base of columella more marked and shell breadth in apical view parallel to apertural edge greater than that at right angles to it.

Female oviparous; presence of glandular oviduct and absence of brood pouch can be used to separate females of this species from Littorina saxatilis with which it is found. In males the prostate does not extend to level of anus, penial glands frequently extend to or around curved base of penis; ciliated field adjacent to genital tract is neither extensive nor red, as in L. saxatilis .

In upper barnacle and Verrucaria zone, particularly on exposed shores.

Probably widely distributed, in the North Sea only at the east coast of Britain (Distr. L. arcana).