THE OYSTER AND THE OYSTER INDUSTRY. 9 



Connecticut is third with over 4,000,000 bushels. Rhode Island, 

 New York, New Jersey, and Louisiana produce over 1,000,000 

 bushels annually. 



DESCRIPTION AND ANATOMY.« 



CLASSIFICATION. 



The oyster of commerce in the United States, with the exception 

 of certain parts of the Pacific coast, is the so-called "eastern oyster," 

 belonging to the species Ostrea virginica, Gmelin. It is a member 

 of the group of molluscs popularly known as bivalves, since it has 

 two valves, or shells, which are joined at the narrower ends by a 

 hinge. 



EXTERNAL APPEARANCE. 



The figures in Plates I, XX, and XXI, though reduced in size, 

 give an idea of the usual shape and appearance of the oyster. The 

 average length of the shells of the marketable size is about 5 inches. 

 Oysters, however, may grow to much greater dimensions, and under 

 certain conditions of growth, such as crowding or development on 

 a mud bottom, are forced into various distorted or elongated shapes. 



The sheU of the adult oyster varies greatly in thickness, ranging 

 in extreme cases from somewhat less than one-fourth inch to an 

 inch and one-fourth. The usual thickness is from one-fourth to 

 thi'ee-eighths inch, decreasing to paperlike thinness on the margms 

 of a rapidly growmg shell. 



The exterior is marked by laminations and more or less concentric lines of growth; 

 it is often covered by a yellowish cuticle, but is sometimes white and flinty in appear- 

 ance. The inside of the shell is generally white, somewhat tinged mth purple near 

 the margins, and with a more or less pearly luster. The muscular impression is gen- 

 erally nearer to the posterior margin than to the hinge ; it is a well-defined scar, kidney- 

 shaped in specimens of ordinary size, but becoming more elongate in very large indi- 

 viduals; in young specimens it is pale, but it afterwards becomes purple or almost 

 black. The left, or lower, valve is deeply concave within, the upper valve being 

 flat or, usually, slightly concave. The animal portions are large, nearly filling the 

 shell, and the mantle border is comparatively narrow. & 



ANATOMICAL FEATURES. 



The two valves of the shell of the oyster are held together at the 

 hinge by a dark-colored elastic ligament so placed that it tends to 

 throw the free ends of the valves slightly apart when the large 

 muscle of the oyster is cut or relaxed. The main structures of 

 interest making up the body of the oyster are shown in Plate II and 

 in text figure 1. Plate II represents an oyster lying in the left valve, 

 which is deeper than the right, and more cup-shaped. This is also 

 nearly always the valve by which the oyster is attached to rocks, etc. 

 The flatter right valve is represented as having been removed. The 

 narrow part of the oyster is the anterior or front end, the mouth 

 being located in that region. The broad part is the posterior or 

 rear end. The back or dorsal side is at the top of the picture and 

 the ventral or under side below. The oyster, however, bemg at- 

 tached by its left side, may rest in the water in any conceivable 

 position, depending on the surface to which it has fastened itself. 



"The brief account of the anatomy and life history of the oyster is based chiefly on the researches of 

 Brooks (1895), Julius Nelson ( lSSS-1893 and 1900-1915), and Staflord (1913). 

 6 Moore, H. F. (1S97, p. 266.) 



