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Rh the outside of the body whorl only in the region behind the slightly flaring lip. 3 other cords are present just below the suture. Columella area dished; reinforced by the round, pillar-like columella. A small pimple is present near the posterior canal in the aperture. Outer lip with strong crenulations on the inside. Periostracum a soft gray-black felt. A common littoral species in the West Indies which bears its young in a brood pouch. Rare in Florida.

Modulus modulus Linné

Atlantic Modulus Plate 21f; figure 38 Florida to Texas and the West Indies.

About ½ inch in length. Characterized by the small, projecting, tooth-like, frequently brownish spine located on the lower end of the columella. Base of shell with about 5 strong, spiral cords. Top of whorls with low, slanting, axial ribs. Color grayish white with beach-worn specimens often exhibiting flecks of purple-brown. Found abundantly among weeds in shallow, warm waters.

Modulus carchedonius Lamarck, the Angled Modulus (Caribbean area) lives in deeper water, and differs in having the periphery of the shell well-angulated, the spiral cords smaller and neater, in lacking the strong, axial ribs, and in never having the columella tooth colored. Not too common.