44 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [338] 
The only Annelid observed high up on the sand-beaches is the slen- 
der, white Halodrillus littoralis, referred to on page 324, which lives 
under the decaying sea-weeds in great numbers. 
On the lower parts of the sand-beaches, toward low-water mark, and 
especially on the broad flats, which are barely uncovered by the lowest 
tides, a much larger number of species occurs. 
Among the Crustacea of these sandy shores we frequently find the 
common Cancer irroratus, (p. 312,) which is very cosmopolitan in its 
habits. Occasionally we meet with a specimen of Carcinus granulatus, 
bat this is not its favorite abode; but the “lady-crab” or ‘sand-crab,” 
Platyonichus ocellatus, (Plate I, fig. 4,) is perfectly at home among the 
loose sands at low-water mark, even on the most exposed beaches. This 
species is also abundant on sandy-bottoms off shore, and as it is furnished 
with swimming organs on its posterior legs, it can swim rapidly in the 
water and was taken at the surface in Vineyard Sound in several in- 
stances, and some of the specimens thus taken were of full size. When 
living at low-water mark on the sand-beaches it generally buries itself 
up to its eyes and antenne in the sand, watching for prey, or on the look- 
out for enemies. If disturbed it quickly glides backward and down- 
ward into the sand and disappears instantly. This power of quickly 
burrowing deeply into the sand it possesses in common with all the 
other marine animals, of every class, which inhabit the exposed beaches 
of loose sand, for upon this habit their very existence depends during 
storms. By burying themselves sufliciently deep they are beyond the 
reach of the breakers. The means of effecting this rapid burrowing are 
very diverse in the different classes. Thus one of the fishes (Ophidium 
marginatum), which lives in these places, has a long acute tail and by 
its peculiar undulatory motions can instantly bury itself tail-first in the 
sand. Others have’acute heads and go in head-first. . 
The “lady-crab” is predacious in its habits, feeding upon various 
smaller creatures, but like most of the crabs it is also fond of dead 
fishes or any other dead animals. In some localities they are so abun- 
dant that a dead fish or shark will in a short time be completely covered 
with them, but if a person should approach they will all suddenly slip off 
backwards and quickly disappear in every direction beneath the sand; 
after a short time, if everything be quiet, immense numbers of eyes 
and antennz will be gradually and cautiously protruded from beneath 
the sand, and after their owners have satisfied themselves that all is 
well, the army of crabs will soon appear above the sand again and con- 
tinue their operations. The color of this crab is quite, bright and does 
not imitate the sand, probably owing to its mode of concealment. 
The ground-color is white, but the back is covered with annular spots 
formed by specks of red and purple. Itis devoured in great numbers 
by many of the larger fishes. 
Another curious burrowing creature, living under the same circum- 
Stauces as the last, is the Hippa talpoida, (Pate II, fig. 5.) But this 
