GEOGRAPHY OF CENTRAL FLORIDA 165

 The larger lakes have sandy beach ridges on their more exposed shores, and sand-bars forming across their embayments, as in lakes with sandy shores the world over, but none of our lakes are large enough to have any perceptible development of dunes around them. Wave-cut cliffs are exhibited on a small scale in the clay bluffs on the southeast side of Lake Weir, and perhaps on other.lakes.
 Minor topographic forms. In many places close to the Indian River, St. John's River, Tampa Bay, and other navigable waters there are shell mounds several to many feet high and usually an acre or less in extent, which are commonly supposed to be'Indian "kitchen middens," though the possibility of some of them having been partly built up by raccoons or other four-footed animals does not seem to have been wholly eliminated. Some are composed chiefly of oysters and others of other mollusks, especially along rivers, where there are no oysters. One on the east side of the Indian River about opposite Melbourne (fig. 34), which is being excavated for road material (a fate shared by many others), shows about ten feet of shells, nearly all Chione cancellata, a small clamlike bivalve, resting on yellowish sand. There are thin layers of humus among the shells every few inches, presumably indicating that the growth of the mound was frequently interrupted long enough for a little vegetation to grow on it. Some of the mounds have more sand than shells in them, and must have been formed in a somewhat different manner; but the subject has not been sufficiently investigated.
 Terraces (?). The boundary between flatwoods and uplands is sometimes gradual and sometimes rather abrupt, as for example at or near Bronson, DeLand and Lake Helen. In recent years these abrupt scarps have been regarded by some geologists as Pleistocene, shore lines, or terraces,* but they do not appear to be continuous for any great distance, as terraces should be, and they lack some of the characteristic features of shore-lines, such as dunes.

 *See Matson & Sanford, U. S. Geol. Surv. Water Supply Paper 319 (1914), pP. 31-35, 210-211, and map (plate 5) ; and comment on same in Geog. Revew 4:224-225. 1917.