Closely allied to /Littorina/ is the genus /Lacuna/, one species of which, ^L. vincta^, is very abundant on the New England coast. A curious and distinguishing feature of this genus is the umbilicus, which forms a lengthened groove along the columella. /L. vincta/ rarely exceeds one half of an inch in length, and is thin, with a pointed spire of five whorls. It is either of a uniform horn-color, or purplish, or banded with chestnut. It may best be found upon marine plants in sheltered places, or may sometimes be gathered in quantity from the roots of /Laminaria/ washed in by storms. GENUS ^Tectarius^ The specific representatives of this genus are mostly tropical. ^T. nodulosus^ is abundant in Florida. It is about one half of an inch long, and has the flattened columella and round mouth characteristic of /Littorina/. It is decorated somewhat elaborately by revolving rows of nodules which cover the entire shell. Its station and habits are the same as those of /Littorina/. FAMILY ~CERITHIIDÆ~ In this family we meet with a somewhat new type of shell—the long, turriculate shell, with many whorls and with a channeled [pg374] aperture. The /Cerithiidæ/ include a large number of genera, mostly tropical in distribution. Their shells are usually highly ornamented in various schemes of sculpture, but they lack beauty in color. The animal is provided with a siphon, as is indicated by the anterior canal of the shell. The operculum is corneous, with a nearly central nucleus. GENUS ^Cerithium^ ^C. floridanum.^ A very common species on the west coast of Florida, also sparingly found at Hatteras. It has eight or ten whorls, a gradually tapering spire, and a sharp apex; the aperture is oblong, with a deeply cut anterior canal projected to the left and backward (when the specimen is held apex up, with the aperture toward the observer). The sculpture is elaborate, consisting of many rows of revolving ribs, and close to the suture there are circling rows of nodes. There is a curious hump just to the left of the aperture, which is quite characteristic of the genus. The color is whitish-gray; the length one and a quarter to one and a half inches. Station, shallow water in lagoons and sheltered spots. (Plate LXIX.) ^C. muscarum.^ Another Floridian species, somewhat smaller than the last (one inch in length). It has heavy, prominent, transverse ribs crossed by circling rows of chestnut spots, one heavy revolving rib around the base; eight or nine whorls; a high-tapering spire; and a sharp apex. The aperture is oblong, with the anterior canal projecting to the left. The columella is arched; the color shining gray to very light purplish. This very pretty little shell may be gathered literally by the shovelful all along the west Florida coast in sheltered spots, on sandy and shallow bottoms. (Plate LXIX.)