34 BULLETIN OF THE BUREAU OF FISHERIES 



There are other species of hydroid medusas 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 larva? 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 a?n<znus 11 ) 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 zceae 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 larvae ; 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. 



is Crab larvse also were plentiful 38 miles o2 Cape Cod and on Georges Bank August 12 to 19, 1926. 



