ABSTRACT
Intensive shell collecting by eighteenth and nineteenth-century naturalists in the English, Spanish, French, Portuguese, and Dutch tropical colonies resulted in the discovery of an overwhelming number of spectacular new species and genera. A formal framework for the study of worldwide biogeography was first proposed in two contemporaneous books, both published in 1856. The concept of broad, generalized faunal regions was challenged in the 1970s, primarily in the works of James Valentine. Traditionally, tropical seas are defined as low latitude systems that have surface water temperatures that never fall below 20 degrees Celsius. Bodies of water that house most, if not all, of these index families and subfamilies as components of resident molluscan assemblages are referred to as Eutropical Seas. Environmentally, eutropical areas are demarcated by the presence of coral reefs and their associated carbonate sediments, by Turtle Grass (Thalassia) beds, and by peripheral mangrove tree forests.
