Page:American Seashells (1954).djvu/190

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 * AA. Periphery rounded or indistinctly rounded.
 * &emsp;B. Surface spirally striate:


 * CC. Umbilical callus strong, slightly convex:


 * BB. No Spiral striations.
 * &emsp;C. Diameter 1.8 to 2.2 mm.:


 * DD. Depressed, h/d ratio about 50:

$3/4$ to 1 inch in length, elongate, $1/4$ as wide; 8 to 10 rounded whorls. No umbilicus. Aperture round; columella smooth, slightly arched. Whorls with 5 to 6 smooth, flat-topped, spiral cords between sutures. Color cream to chalky-white, with a thin, polished, gray-brown periostracum. Operculum round, multispiral, chitinous, dark-brown. Common from 10 to 75 fathoms.

T. reticulatum Mighels (Arctic Ocean to Maine; and Alaska) is similar,