1: ribs have sloping surface with raised adapical edge. 2: intervening furrows wide and shallow. Other identification criteria used for specimen M. Filament of penis long and tapering without mucronate tip on un-anaesthetized live specimen (see M8599 <a href="https://marinvert.senckenberg.s…

White penis filament clearly visible above animal’s back; long, slender, steadily tapering to a non-mucronate tip. Not anaesthetised; see P8560. Other identification criteria used for specimen M Previous work by Hannaford Ellis on the same shore as this find showed that L. arcan…

Multicoloured specimen with spiral lines; might cause misidentification as Littorina compressa if recorder unaware that dark spiral lines are not diagnostic for that species. Previous work by Hannaford Ellis on the same shore as this find showed that L. arcana were thin-shelled…

Most features seen through translucent mantle. 1: kidney. 2: rectum. 3: ctenidium (gill). 4: cephalic tentacle. 5: ovary. 6: developed pallial oviduct, not brood pouch with shelled embryos. 7: operculum. Feature 6 is diagnostic for differentiation from L. saxatilis s.s.; see L. arcana …

Left: proximate (inner) face, visible if mantle cut open. Right: distal (outer) face; side seen through mantle when animal extracted from shell. 1: anus. 2: rectum. 3-6: pallial oviduct. 3: opening of oviduct 4: jelly gland (parallel septa faintly visible in left view). 5: albumen gland. 6: capsule…

1: rectum. 2: reduced prostate (post breeding?). 3: area without ciliated field, usually occupied if L. saxatilis s.s.. 4: ribbed orange ciliated field along edge of prostate. 5: reduced penis (post breeding?). 6: back of head. Note: ciliated field is in correct position, but larger than expe…

Grey shell with partial white band from well defined site where previous workers found 100% of Rough periwinkles were Littorina arcana (Dytham, Grahame & Mill, 1990). Though perhaps not statistically significant, among over 20 000 Rough periwinkles at seven sites, they found only ten grey…

1: rectum. 2: well developed pallial oviduct with transverse septa in jelly gland and, at posterior, opaque white albumen gland. (No brood pouch with embryos). No ciliated field detectable next to oviduct or near anus. 3: back of head. Feature 2 is diagnostic for differentiating L. arcana fr…

Live male with extended yellowish-white penis; long, slender, steadily tapering to a non-mucronate tip. Not anaesthetised. Inset of same penis at same scale, contracted and distorted by boiling. Hannaford Ellis (1979) states: “The range of variation of the penis morphology seen in L. arcana</i…

Filament of penis folded forward at 1. 2: non-mucronate tip of penis. Explanation of “mucronate” at eflora.library.usyd.edu.au/glossary/mucronate Wide grey dorso-lateral bands on cephlic tentacles separ…

1: ribs have sloping surface with raised adapical edge. 2: intervening darker furrows wide and shallow. Other identification criteria used for specimen P. Filament of penis long and tapering without mucronate tip on un-anaesthetized live specimen (see P8560). Previous work by Hannaford Ell…

Yellowish-white penis extended, curved over body, dorsal edge in view; filament long, thin and tapering steadily to non-mucronate tip. Explanation of “mucronate” at eflora.library.usyd.edu.au/glossary/mucron…

PROVISIONAL text. I have found great variation and contradiction in paper & online sources. Your comments would be appreciated. In particular, last 3 lines about layer 3 are based on my examination of the disposition of the layers and on reasoning unsupported by any source that I can find…