74 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [365] 
numbers in the somewhat brackish waters of estuaries and the mouths 
of rivers. The young specimens of all sizes, up to two or three inches 
in breadth, are, however, very frequent along the muddy shores, hid- 
ing in the grass and weeds or under the peaty banks at high-water, and 
retreating as the tide goes down; when disturbed they swim away 
quickly into deeper water. They also have the habit of pushing them- 
selves backward into and beneath the mud for concealment. They are 
predacious in their habits, feeding upon small fishes and various other 
animal food. They are very pugnacious and have remarkable strength 
in their claws, which they use with great dexterity. When they have 
recently shed their shells they are caught in great numbers for the 
markets, and these “soft-shelled crabs” are much esteemed by many. 
Those with hard shells are also sold in our markets, but are not valued 
so highly. This crab can easily be distingushed from all the other 
species found in this region by the sharp spine on each side of the 
carapax. 
The common “ spider-crab,” Libinia canaliculata, (p. 339,) is very com- 
mon on muddy shores and flats. It hides beneath the surface of the 
mud and decaying weeds or among the eel-grass, and is very sluggish 
in its motions. Its whole surface is covered with hairs which entangle 
particles of mud and dirt of various kinds; and sometimes hydroids, 
alge, and even barnacles grow upon its shell, contributing to its more 
ready concealment. The males are much larger than the females, and 
have long andstout claws. They often spread a foot or more across the 
extended legs. The females have much smaller and shorter legs and 
comparatively weak claws. 
Another similar species, Libinia dubia, is also found on muddy shores 
and has nearly the same habits. It has a much longer rostrum, more 
deeply divided at the end. 
The two common species of ‘* hermit-crabs” are both found on muddy 
shores, especially among eel-grass, but the larger one, Hupagurus polli- 
caris, (p. 313,) is comparatively rare. The small one, ZH. longicarpus, (p. 
313,) is very common and usually occupies the dead shells of Ilyanassa 
obsoleta, though many may be found in other species of shells. 
The Gebia affinis (Plate I, fig. 7) isa crustacean somewhat resembling a 
young lobster three or four inches in length. It lives on muddy shores 
and digs deep burrows near low-water mark, in the tenacious mud or clay, 
especially where there are decaying sea-weeds buried beneath the sur- 
face. The burrows are roundish, half an inch to an inch in diameter, 
very smooth within, and go down obliquely for the distance of one or 
two feet, aud then run off laterally or downward, in almost any direc- 
tion, to the depth of two or three feet, and are usually quite crooked 
and winding. We have found them most abundant on the shore of 
Great Egg Harbor, New Jersey, near Beesley’s Point, but they also 
occur at New Haven and Wood’s Hole, &c. This species is quite active ; 
it swims rapidly and jumps back energetically. It is eagerly devoured 
