THE OYSTER CRAB. 765 



burrows either aide may go in advance, but the male more commonly comes out with the large 

 claw forward. According to Mr. Smith's observations this species is a vegetarian, feeding upon 

 the minute algse which grows upon the moist sand. In feeding, the males use only the small 

 claw, with which they pick up the bits of algae very daintily ; the females use indifferently either 

 of their small claws for this purpose. They always swallow more or less sand with their food. 

 Mr. Smith also saw these Crabs engaged in scraping up the surface of the sand where covered 

 with their favorite algse, which they formed into pellets and carried into their holes, in the same 

 way that they bring sand out, doubtless storing it until needed for food, for he often found large 

 quantities stored in the terminal chamber." 



As above stated, the Fiddler Crabs are sometimes used as bait; and at the mouth of the 

 Mississippi River 0. pugnax, has been observed, in connection with the river Cray-fish [Gambarus), 

 burrowing into and greatly damaging the levees. 



Yellow Shoeb-orab of the Pacific coast — Hetekograpstjs oeegonensis, Stm. 



Purple Shore-crab of the Pacific coast — Heterograpsus nudus, Stm. 



According to W. N. Lockington, these two species are by far the most abundant of all the 

 California coast Crabs; but they are only eaten by the Chinese. The body of these Crabs is 

 nearly square, and the claws large in proportion. In H. oregonemis the anterior half of the 

 lateral margins on each side has two rather deep indentations, resulting in the formation of two 

 large spine-like projections, which bend strongly forward; in S. nudus these characters are less 

 pronounced. The four posterior pairs of limbs in jff. oregonensis are also more or less hairy, 

 while in ff. nudus they are naked. The general color of the former species is yellow, of the 

 latter purple; H. nudus also has marbled hands and attains a somewhat larger size than H. 

 oregonensis, measuring at times two inches broad. Hundreds of one or other of these species of 

 both sexes and of all sizes may frequently be found together, congregated under a single stone. 

 H. oregonensis is especially abundant in muddy sloughs of salt or brackish water, where it 

 literally swarms. Hundreds of uplifted threatening claws welcome the intruder who ventures 

 near these mud flats when the tide is out. Both species occur at Puget Sound, and range thence 

 southward to the southern limit of California. H. nudus also occurs at the Sandwich Islands. 

 Both species are eaten to some extent by the Chinese, who spit them on wires and cook them 

 over their fires. 



The Oys^ter-crab — PmNOTHERES osTREUM, Say. 



" The ' Oyster-crab,' Pinnotheres ostreum, is found wherever oysters occur. The female lives, 

 at least when mature, within the shell of the oyster, in the gill cavity, and is well known to most 

 consumers of oysters. The males are seldom seen, and rarely, if ever, occur in the oyster. We 

 found them, on several occasions, swimming actively at the surface of the water in the middle of 

 Vineyard Sound. They are quite unlike the females in appearance, being smaller, with a firmer 

 shell, and they differ widely in color, for the carapax is dark brown above, with a central dorsal 

 stripe and two conspicuous spots of whitish ; the lower side and legs are whitish. The female has 

 the carapax thin and translucent, whitish, tinged with pink." ' 



This Crab has been recorded from the Atlantic coast from Massachusetts to South Carolina. 

 The females measure, when adult, about half an inch broad and a little less in length. From the 

 European Oyster-crab {Pinnotheres pisum) our species differs in having a thinner and more, 

 membranaceous shell and a larger size. The colors are also different in the two species.' 



' Vbrrill: Vineyaid Sound Report, p. 367, 1871-'72. 



