On this form, well-developed, thick, porcellaneous interior layers conceal outer shell so “marginal rays are never conspicuous” internally (Fretter and Graham, 1994), and features defined by orange staining and differences of reflectivity/translucence (resulting from differences in crystal-form of shell-material made by different parts of mantle) are clearly visible.

1: aperture rim, minute (or absent) part of pigmented exterior shell-layer; secreted by mantle-edge.
2: wide peripheral “skirt layer” that reflects light, often iridescing blue, from many short crystalline lines parallel to rim; secreted by mantle-skirt.
3: narrower, matt, opaque, “pallial groove-band”; secreted by mantle roofing groove that contains the gills.
4: translucent, horseshoe-shape “pedal-retractor muscle scar”; mark left by muscle attachment.
5: very thin “anterior mantle-attachment scar” connecting ends of pedal-retractor scar; mark left by muscle attachment.
6: central “amphora area” enclosed by scars 4 & 5; secreted by mantle over visceral hump.
7: short mark across pallial groove-band where efferent pallial vessel enters nuchal cavity through gap in pallial gills.
8: excavated elliptical pit; as all pits have same shape, probably caused by parasitic or inquiline organism, one has displaced end of horseshoe-shaped pedal-retractor muscle.

OTHER SPECIES ALBUMS
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