BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
357 
the data at hand and one which is more often taken along the region near the tide 
lines. It has been caught very seldom on our cruises, probably because these cruises 
were confined to the offshore waters. 
Three specimens only were taken — one at area Z in December, 1915 (depth, 17 
meters), another at area I in January, 1921 (depth, 12 meters; salinity 13.19 per mille 
at bottom; temperature, 3.4° C. at bottom), and a third at area V in March, 1921 
(depth, 14 meters; salinity, 11.32 per mille at bottom; temperature, 9.6° C. at bot- 
tom). All of these specimens were captured on the winter and spring cruises and 
none on the summer cruises. The same condition, we shall see, holds true for Palae- 
monetes vulgaris, another shore form, but not for Crago septemspinosus , which frequents 
deeper water. The United States National Museum has another lot of P. carolinus 
consisting of a rather large number of specimens (over 289) evidently collected near 
the shore by collectors not connected with our survey. All of these specimens with 
the exception of two were taken during the summer months, and it might be inferred 
that in the winter this species migrates into deeper water, but the absence from the 
lot just mentioned of any specimens collected during the winter time may be due to 
the fact that ordinarily collectors do not go on trips at that time of the year. While 
the capture of some specimens of P. carolinus during our winter and spring cruises 
and our failure to find any specimens on the summer and fall cruises favors the plausi- 
ble assumption that there is migration of this form from the shallow, cold water to 
the deeper, warm water during the colder months and vice versa with the approach 
of the warmer season, there is still insufficient evidence to establish it as a fact. 
It is clear from data collected by the United States National Museum that 
Palaemonetes carolinus is found ordinarily in shallow water and that it flourishes in 
water of very low salinity. Specimens have been collected at various places along 
the western shore of Chesapeake Bay in Maryland and also well up in the rivers — for 
example, at St. George Island, Lower Machodoc Creek, and Blakistone Island, which 
are, respectively, 10, 20, and 25 miles up the Potomac River. Collections have been 
made also at Island Creek, which is 12 miles up the Patuxent River. 
Undoubtedly this species may be found along the shores and in the rivers of the 
eastern shore of Chesapeake Bay, although none has been recorded from that region. 
It has been collected, however, at Smiths Island, Northampton County, Va., prob- 
ably close to shore, just outside of the mouth of the bay, and there is good reason to 
believe that it will be found close to shore and in the rivers of the lower part of the bay. 
Little is known of the breeding habits of Palaemonetes carolinus except that 12 
ovigerous specimens were collected 20 miles up the Potomac River, in Lower Macho- 
doc Creek, during July, 1919. Evidently, then, this species, like many others, breeds 
during the summer. 
Palaemonetes vulgaris, the commmon shrimp or prawn, occurs along the whole 
eastern coast of the United States but is especially abundant in bays and estuaries 
(Say, 1817). Like P. carolinus, it was taken infrequently on our cruises but some- 
what more often than that species. All of the adult specimens were caught at areas 
located in the region between the mouth of the Potomac River and the mouth of the 
bay. However, the United States National Museum has specimens in their collection 
which have been found in various places all over the bay from the region of Love 
Point to Cape Charles City, but practically all of these specimens were collected in 
shallow water near the shore. Neither our records nor those of the National Museum 
show that P. vulgaris makes its way far into the rivers. 
