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188 smooth and narrowly channeled. Shell smooth, yellowish white and covered with a thin, yellowish brown periostracum which flakes off when dry. Um- bilicus absent or a very slight slit. Operculum paucispiral, horny, translucent- brown and with microscopic, spiral lines. A moderately common, cold-water species found just offshore down to 70 fathoms. Its counterpart, A. purpurea Dall, common in Alaska, is very similar, but % inch in length and with a greenish and darker periostracum. Oldroyd's Fragile Moon-slieli Figure 4^^- Genus Eunaticina Fischer 1885 Eunaticina oldroydi Dall Oregon to San Diego, California. 1/4 to iVi inches in length, resembling Lunatia leivisi, but much lighter in weight, with a more pointed spire, without the heavy, brownish callus and having, instead, the upper part of the columella expanded into a white, thin area which partially obscures the umbilicus. Micro-sculpturing on shell exte- rior is prominent. Moderately common; dredged offshore 30 to 70 fathoms.

Figure 43. a, Polifiices draconis Dall, 2 inches (Pacific Coast); b, Natica clausa Bred, and Sby., i inch (Arctic waters); c, Jjiimtia pallida Bred, and Sby., 1^-2 inches (Arctic waters); d, Lamellaria diegoensis Dall, Y^ irich ( Calif oi-nia); e, Eunaticina oldroydi Dall, 2 inches (Pacific Coast).