338 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



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 Caroimis granulatus, 

 but this is not its favorite abode ; but the u 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 antennae 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 sufficiently 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 (Ophidinm 

 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 antennae will be gradually and cautiously protruded from beneath 

 the sand, aud 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. It is devoured in great numbers 

 by many of the larger fishes. 



Another curious burrowing creature, living under the same circum- 

 stances as the last, is the Hijpjpa talpoida, (Pate II, fig. 5.) But this 





