Page:American Seashells (1954).djvu/175

Rh 2 to 3 inches in length; characterized by a strong, wavy, overhanging periphery, and by the dark-brown, fuzzy periostracum. Base concave, with 3 small, indistinct spiral cords. Outside of operculum with 3 strong, prickly ridges. Common in shallow water, especially around Todos Santos Bay, Lower California.

$1 1/2$ to 3 inches in length, heavy, brick-red to reddish brown in color. Characterized by 5 to 6 strong, spiral cords on the flattish base. Operculum chitinous green on inner side; outer side swollen, smooth, enamel-white. Formerly A. inaequalis Martyn. Moderately common just offshore down to 40 fathoms.

Shells small, turbinate in shape. Operculum calcareous, oval, thick; its exterior with a thick, paucispiral whorl. Underside of operculum convex with multispiral, chitinous whorling. Leptothyra Pease 1869 is this genus.