THE AMERICAN OYSTER CRASSOSTREA VIRGINICA GMELIN 



By Paul S. Galtsoff, Fishery Biologist 

 Bureau of Commercial Fisheries 



CHAPTER I 

 TAXONOMY 



Page 



Taxonomic characters - ..- 4 



Shell 4 



Anatomy.- 4 



Sex and spawning. 4 



Habitat 5 



Larval shell (Prodissoconch). 6 



The genera of living oysters 6 



Genus Ogtrea 6 



Genus Crassostrea. 7 



Genus Pyaiodonie 7 



Bibliography... 14 



The family Ostreidae consists of a large number 

 of edible and nonedible oysters. Their distribution 

 is confined to a broad belt of coastal waters within 

 the latitudes 64° N. and 44° S. With few excep- 

 tions oysters thrive in shallow water, their vertical 

 distribution extending from a level approximately 

 halfway between high and low tide levels to a 

 depth of about 100 feet. Commercially exploited 

 oyster beds are rarely found below a depth of 40 

 feet. 



The name "Ostrea" was given by Linnaeus 

 (1758) to a number of mollusks which he described 

 as follows: 



"Ostrea. Animal Tethys, testa bivalvis in- 

 aequivalvis, subaurita. Cardo edentulus and 

 fossula cava ovata, striisque lateralibus transversis. 

 Vulva anusve nuUus." The name Tethj-s (from 

 Greek mythology and also refers to the sea) 

 applies to the type of marine animals, living either 

 witliin the shells or naked, that Linnaeus listed 

 under a general name "Vermes" which includes 

 worms, mollusks, echinoderms, and others. The 

 translatioiKjf Linnaeus' diagnosis reads as follows: 

 Shell bivalve, unequal, almost ear-shaped. Hinge 

 tootldess, depression concave and oval-shaped, 

 with transverse lines on the sides. No vulva or 

 anus. 



XuTK. — Approved for publication April 24, 1904. 

 FISHERY bulletin: VOLUME 64, CHAPTER I 



This broad characterization included a number 

 of genera such as scallops, pen shells (Pinnidae), 

 limas (Limidae) and other mollusks which ob- 

 viously are not oysters. In the 10th edition of 

 "Systema Naturae," Linnaeus (1758) wi'ote: 



"Ostreae non omnes, imprimis Pectines, ad 

 cardinem interne fulcis transversis numerosis 

 parallelis in utraque testa oppositis gaudentiquae 

 probe distinguendae ab x\rcis poly pie pto(jinglymis, 

 cujus dentes numerosi alternatim intrant alterius 

 sinus." i.e., not all are oysters, in particular the 

 scallops, which have many parallel ribs running 

 crosswise inward toward the hinge on each shell 

 on opposite sides; these should properly be dis- 

 tinguished from Area polyleptoginylymis whose 

 many teeth alternately enter between the teeth 

 of the other side. 



In the same publication the European flat 

 oyster, Ostrea edulis, is described as follows: 

 "Vulgo Ostrea dictae edulis. 0. testa semi- 

 orbiculata membranis imbricatis undulatis: 

 valvula altera plana integerrima." i.e., commonly 

 called edible oyster; shell semicircular, outer valve 

 with wavy grooves; the other small valve com- 

 pletely flat. With a minor change Linnaeus' 

 diagnosis is repeated by Gmelin (1789). 



Lamarck (1801) restricted the family Ostreidae 

 to the species of the genus Ostrea which was 

 characterized by him as follows: Adhering shell, 

 valves unequal, irregular, with divergent beaks 

 which with age become very unequal; the upper 

 valve becomes misplaced. Hinge without teeth. 

 Ligament half internal, inserted in the cardinal 

 lunule of the valves; the lunule of the lower 

 vah-e and the beak grow with age and sometimes 

 reach great length. 



Great confusion in the usage of the generic 

 name of living oysters resulted, however, from 



1 



