Page:American Seashells (1954).djvu/217

is white in color (although the periostracum is yellow-brown), with more prominent spiral threads, and with coarser spiral threads in the young. Found offshore. Hipponix barbatus Sowerby (Bearded Hoof-shell) from the same region is limpet-shaped, with coarse, nodulated ribs which are largest on the anterior slope of the shell. The edge of the shell is strongly serrated with cut lines. The periostracum is very shaggy especially on the middle of the anterior slope. Common. Family VANIKOROIDAE Genus Vanikoro Quoy and Gaimard 1832 Vanikoro oxychone Morch West Indian Vanikoro Southeast Florida and the West Indies. Vz inch in length, solid, strong and pure white. With 3 whorls. Charac- terized by its large aperture, by its deep, narrow, arched umbilicus and straight, rounded, pillar-like columella and by the 10 or 12 beaded, spiral cords on the last whorl. Small axial threads tend to give a slightly cancellate sculpture. Apex glassy and smooth. Suture well-indented. Uncommon in shallow water. Superjamily CALYPTRAEACEA Faimly TRICHOTROPIDAE Genus Trichotropis Broderip and Sby. 1829 Trichotropis borcalis Broderip and Sowerby Boreal Hairy-shell Plate 24d Arctic Seas to Maine. Arctic Seas to British Columbia. V2 to % inch in length, with 4 to 5 carinate whorls. Shell not very strong, chalky-white and covered with a thick, brownish periostracum which has hairy spicules on the region of the shell's 3 major spiral cords. UmbiHcus chink-like, bordered by a large, spiral cord. Spire usually eroded badly. Numerous, crowded axial threads present. A common cold-water species found from below low water to 90 fathoms. Trichotropis cancellata Hinds Cancellate Hairy-shell Plate 24b Bering Sea to Oregon. % to I inch in length, 5 to 6 rounded whorls bearing between sutures 4 to 5 strong spiral cords, between which there may be small axial ribs which produce a cancellate sculpturing. Spire high, rather pointed. Aperture a little