[475] INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 181 
Island, and Connecticut. It is, therefore, probable that the total amount 
taken on the coast north of Cape Hatteras is not less than 30,000,000 
bushels annually, having a value of more than $20,000,000. In making 
this estimate we should allow for the great increase in bulk and value 
of many of the Maryland and Virginia oysters that are transplanted to 
northern waters, and allowed to grow before using. The average value 
of the northern oysters, both native and transplanted, is probably more 
than seventy-five cents per bushel. It is, therefore, probable that the 
above estimate is considerably too low. 
The great oyster-markets of the country are Baltimore and New York. 
In Baltimore immense quantities of oysters are put up in kegs and 
cans to supply the distant parts of our own country and also to ship 
to nearly all foreign countries. In 1867 it was estimated that more 
than 10,000 persons were employed in this branch of the business. 
There were then thirty packing-houses, employing 4,500 openers. In ad- 
dition to the packing business great quantities of oysters are sold at Bal- 
timore and sent away in the shell. The total quantity sold at Baltimore 
exceeded 7,000,000 bushels, of which about 5,000,000 bushels came from 
Maryland waters, and the balance from Virginia, Of these over 
1,000,000 bushels were sent to New York, 700,000 to Fair Haven, Con- 
necticut, where an extensive packing business is carried on, 450,000 
to Philadelphia, 550,000 to Boston. 
The oyster trade of New York, several years ago, was estimated at 
over $8,000,000, employing 2,500 vessels, and it has greatly increased 
since that estimate was made. 
Among the most common shells that are found attached to oysters 
are Orepidula fornicata (Plate XXUI, figs. 129, 129a) and C. unguiformis, 
(Plate XXII, fig. 127.) They both occur together on the upper as well 
as the under valves, and in all cases retain their ordinary characters, 
except that the latter is more regular in form, and usually has the 
upper surface slightly convex, instead of being much distorted and 
with a concave upper surface, as the larger specimens that live on 
the inside of dead univalves usually are. Its color, when living on the 
oysters, is always white, while the C. fornicata is always more or less 
marked with brown. 
The common muscle, Mytilus edulis, (p. 307) frequently occurs attached 
to oysters, and when it accumulates on the oyster-beds in large quan- 
tities it is very injurious. The Modiola hamatus (p. 374) is a very pe- 
culiar-looking muscle, having a broad, often hatchet-shaped, distorted 
shell, covered with prominent radiating ribs, many of which are forked. 
Its color is yellowish or brownish. It somewhat resembles Modiola plica- 
tula, but is broader and has coarser ribs. This muscle is sometimes 
found in New Haven Harbor, living on the oyster-beds in considerable 
numbers, and of full size, attached to the oysters, either singly or in 
clusters, by the byssal threads. It has been observed only in the sum- 
mer and fall and it may not have survived the winters, for it is possible 
