(b) Bivalvia (= Conchae): Mya, Solen, Tellina, Cardium, Mactra, Donax, Venus, Spondylus, Chama, Arca, Ostrea, Anomia, Mytilus, Pinna.
The Senonian consists of a central facies with Micraster peini; a meridional facies with Ostrea; and a northern facies developed round Tunisia with large forms of Inoceramus and echinoids.
The Middle Eocene is characterized by the presence of Ostrea bogharensis and the Upper Eocene by highly fossiliferous sandstones and marls.
At the close of the Lower Miocene period (beds with Ostrea crassissima) great modifications in the relief and limits of the Algerian formations took place.
- Development of the Oyster, Ostrea edulis.
It has been conclusively shown that the Ostrea edulis does not fertilize itself.
The use of this name in the vernacular is equivalent to that of Ostrea (Lat.
D irpEov, oyster, so called from its shell, 66TEOV, bone, shell) in zoological nomenclature; there are no genera so similar to Ostrea as to be confounded with it in ordinary language.
Ostrea is a genus of Lamellibranch Molluscs.
In what follows the species of the European coasts, Ostrea edulis, is under consideration.
Westward of and above these strata, the Middle and Upper Jurassic formations are found (Lias, Lower Oolite, Oxfordian, &c.), with well-marked and numerous fossils (Ammonites, Nerinaea, Natica, Astarte, Rhynchonella, Echinodermata, &c.); then the Cretaceous rocks, both these and the Jurassic series being largely developed, the Cretaceous fossils including Nautilus, Belemnites, Ostrea, Gryphaea, &c., and some very large Ammonites (Pachydiscus).
The genus Ostrea has a world-wide distribution, in tropical and temperate seas; seventy species have been distinguished.