34 
BULLETIN OF THE BUREAU OF FISHERIES 
There are other species of hydroid medusae that are not so closely confined to 
shoal water, probably because they are able to pass through their fixed stage at 
greater depths and consequently at a greater distance from land. Staurophora and 
Phialidium, for example, bear much the same relationship to the 100-meter contour 
in their distribution (p. 345) as Aurelia, Melicertum, and other forms more dependent 
on shoal water bear to the immediate coast line. 
Other typical examples of the neritic habit are afforded by the larvae of various 
decapods among the pelagic Crustacea, young crabs, in particular, being instructive 
because so conspicuous and so easily recognized in the tow. These (provisionally 
identified as the common rock crab, Cancer amcenus 17 ) are produced in great numbers 
all along the coast line of the Gulf of Maine in summer, and occasionally they have 
occurred in swarms in our summer hauls near land, for instance, off Rye, N. H., and 
in Ipswich Bay, Mass., on July 23, 1915. Crab larvae of some species are equally 
plentiful on Georges Bank, where we encountered hosts of them on July 23, 1916 
(station 10347), and where Dr. W. C. Kendall towed them in abundance and found 
them providing the young mackerel with a rich food supply at various localities 
along the northern edge of the bank during August, 1896. They are so closely 
limited to the vicinity of the land and to the shallow waters of the offshore banks, 
however, at least so far as occurrence in any numbers is concerned, that I have 
usually sought them in vain in towings made in the central parts of the gulf, even 
during their season of abundance ; nor have we found crab larvae over Platts Bank or 
near Cashes Ledge, though they may be expected there, these doubtess being as good 
crab grounds as is Georges Bank. The presence of an abundance of crab zoeae in the 
surface water of the western basin on August 22, 1914 (station 10254), was an excep- 
tion to the general rule and interesting because the considerable depth (268 meters) 
at the locality in question makes it almost certain that these young crabs were not 
hatched there but had drifted out from the rocky banks and ledges off Cape Ann, 
25 or 30 miles to the west and northwest, which is visible evidence of the circulation 
in this part of the gulf at the time. 18 
Hermit crab (Pagurid) larvae may also swarm locally over the offshore shoals, as 
was the case near Nantucket Lightship on July 25, 1916 (station 10355), when they 
were plentiful in the tow from 30 meters (the total depth of water being 36 meters), 
though represented by occasional examples only at 16 meters and on the surface. 
We have not detected them in any of our hauls in the basin of the gulf, nor are the 
macruran larvae of various species (which are almost invariably present in the 
coastal waters of the gulf in summer) of any importance in the plankton more than 
a few miles from land. 
The larval (naupliid and cyprid) stages of the common barnacle, which appeared 
in myriads along the coast north of Cape Ann in April, 1913 (Bigelow, 1914a), and 
again off Cape Sable during the same month of 1920 (p. 40), are strictly confined to 
shallow waters, for we have never detected them outside the 100-meter contour. 
This applies equally to many other metazoan larvse; those, for example, of the common 
sea anemone (Metridium), which appear in some numbers in our coastwise catches 
17 See Connolly (1923) for account of the larval stages of this crab. 
18 Crab larv* also were plentiful 38 miles off Cape Cod and on Georges Bank August 12 to 19, 1926. 
