National Geographic : 1925 Oct
A PROFILE MAP OF TAHITI SHOWING THE ERODED VOLCANIC CORE, THE LAGOON, FRINGING REEF, AND BARRIER REEF The main body of Tahiti consists of two high land masses connected by a low isthmus. The core of richly carpeted volcanic hills issurrounded by a coastal plain, which reaches a width of as much as a mile only at the mouths of the river valleys. Around thestrand-belt arethefringing reefs, which extend, just awash or slightly submerged, into the lagoon moat (see text, page 363). Principlesofgeographical distribution areillustrated by land snails of the genus Partula.