Fossil Crustacea of the Atlantic and Gulf Coastal Plain
Little has been published concerning the fossil Crustacea of eastern and southern United States. The United States Geological Survey and the United States National Museum have been gradually accumulating specimens, but the sum total is moderate. Crustacean remains, compared to molluscan, are scarce. The shells are thin, fragile, and easily destroyed, so that the remains consist largely of chelae or parts of chelae, as these are usually thicker than the carapace and other appendages. The number of species at hand is relatively small; more are known from the lower Cretaceous of Texas and the Midway of Alabama than elsewhere.
In the Cretaceous the predominating genera of shrimp-like forms are Hophparia and Callianassa-, the former belongs to the family, Homaridae, best known from the common lobster; the latter is a burrowing shrimp of a type which persists at the present day to a limited extent but which in ancient times was noted for the great number of species and individuals. The largest crustacean here recorded occurs in the Comanche series of Texas, a Palaeastacus figured on Plates 3–5. Several species of the genus Linuparus of the family Palinuridae indicate the derivation of Recent L. trigonus of Japan. The three pagurids, or hermit crabs, are referred to genera now living. A prevailing genus of true crabs is Necrocarcinus, a Calappid which became extinct after the Eocene. Fairly abundant are the Gymnopleura or Raninidae, representatives of which still persist in the waters bordering the Coastal Plain. Notable is the presence of two isopods, Aegidae, rare among fossils.