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280 Family RETUSIDAE Genus Retusa Brown 1827 Retusa obtusa Montagu Arctic Barrel-bubble Figure 59a Arctic Seas to off North Carolina. 3 mm. in length, fairly fragile, smooth, stubby and with the spire com- monly slightly sunk or only a little elevated. Columella smooth. A chink- like umbilicus is present. Color translucent-white with yellowish brown stain- ing. Common from shore to 90 fathoms. R. pertejiuis Mighels and R. turrita Moller are this species. Retusa sulcata Orbigny Sulcate Barrel-bubble North Carolina to southeast Florida and the West Indies. 2 mm. in length. Characterized by its small size, fine axial threads, white color, oblong shape, flat sides and deeply sunken spire. Moderately common from 3 to 95 fathoms. Retusa canaliculata Say Channeled Barrel-bubble Plate 26X Nova Scotia to Florida, Texas and the West Indies. 4 to 6 mm. in length, solid, oblong with its spire moderately elevated, but almost invariably eroded. Glossy smooth, except for microscopic growth lines. Outer lip thin, advanced above. Columella of a single, raised, strong spiral ridge. Suture slightly channeled. Nucleus (when present) very small and pimple-like. Color white to cream, commonly with dark, rust-brown staining. Acteocina candei Orbigny is probably only a southern representa- tive of this species. A common shallow-water species which was formerly placed in the genus Acteocina. Genus Pyrunculus Pilsbry 1894 Pyrunculus caelatus Bush Bush's Barrel-bubble Plate 26W North Carohna to southeast Florida. 3 mm. in length, pyriform in shape, rather thick and opaque-white. Spire concealed within a very deep pit. Rather rare from 15 to 43 fathoms. Genus Rhizorus Montfort iSio {Volvula A. Adams, not Gistel) Rhizorus oxytatus Bush Southern Spindle-bubble North Carolina to southeast Florida and Cuba.