450 BULLETIN OF THE BUREAU OF FISHERIES. 



Family OCYPODIDAE. 



Brachyrhyncha having the body more or less distinctly quadrate, the front of 

 moderate width or narrow, the eyestalks usually long and little or no gap between the 

 third maxillipeds. 



This family comprises 14 genera, of which 2 are represented within the Beaufort 

 limits. 



KEY TO THE GENERA OF THE BEAUFORT REGION. 



a. Eyestalks stout; chelipeds of male somewhat unequal Ocypoda. 



aa. Eyestalks slender; chelipeds of male very unequal Uca. 



Genus OCYPODE Weber. 



Ocypode Weber, 1795, p. 92; Fabricjus, 1798, p. 312. 

 Ocypode albicans Bosc. Sand crab. PI. xxxvn, fig. i. 



Ocypode albicans Bosc, 1802, p. 196: Rathbun, 1901, p. 6; Sumner. 1911, p. 675; Fowler, 1912, p. 457, pi. 148, 149. 



Ocypode arenarius Say, 1817, p. 69; Verrill, 1908, p. 306. 



Ocypode arenaria H. Milne-Edwards. 1834-1840, t. u, p. 44; Coues, 1871, p. 122: Kingsley, 1878, p. 322. 



Carapace quadrilateral, convex above from front to back, the sides nearly vertical and the front 

 Strongly deflexed; dorsal region finely granulate on middle and posterior portions, coarsely granulate 

 toward the sides; a raised, dentate ridge marks off the dorsal region from the sides and is continued 

 into a prominent acute angle at the outer comer of the orbit; a similar, but lower ridge extends upward 

 and forward from the base of the fourth leg; orbits very large and open, extending all along the ante- 

 rior margin on either side of the narrow front, both upper and lower margins crested and dentate. 



Eyestalks large, club-shaped; the cornea covering over half the distal article. Antennules and 

 antennae much reduced, the flagellum of the former being hidden beneath the front. Chelipeds, in 

 both sexes and even in the young, unequal, well developed, the larger chela with a vertical stridu- 

 lating ridge of tubercles on tlie inner surface near the base of the movable finger; lower margin of hand 

 thin and serrate; outer surface coarsely tuberculate. Ambulatory legs long, compressed, their margins 

 with numerous tufts of stiff yellow hairs. Between the basal articles of the third and fourth legs, on 

 the venti-al sm^ace, is a hair-fringed breathing slit. 



Measurements of a female: Length of carapace, 42 mm.; mdth, 51 mm. 



Color, gray or grayish white with yellow markings below and on the legs. Young very unlike the 

 adults, being a mottled gray and brown. 



The sand crabs are of the most characteristic animals of the region and occur in abimdance along 

 the ocean beaches and to some extent within the harbor. Their holes, which they dig to a depth 

 from 2 to 4 feet, are to be found in large numbers near the extreme high-tide mark on the outer beaches, 

 in smaller numbers still higher up and occasionally in the dunes, from an eighth to a quarter of a mile 

 from the water. During the heat of the day they keep pretty well to their holes, though it is not at all 

 imusual to find them out in the full glare of the noonday sun, but as evening approaches they sally 

 forth in search of food and probably prowl about dining the greater part of the night. At night they 

 gather by the hundreds along tlie beach just at the edge of the water whence they rush down after each 

 receding wave to pick up fragments of food left on the sand. At such times they enter the water without 

 hesitation but do not go out from the shore more than a few feet. They are, also, to be found high up 

 on the beaches and will gather in numbers about a fire built where they can see it. They vnW approach 

 slowly until the heat becomes evident, then scurry away only to come back and repeat the performance. 



When abroad in the daytime they are alert and are able to distinguish a large moving object a long 

 distance ofi. If one of them is approached it moves away slowly and perhaps will attempt to hide. 

 If it is pursued it runs with great rapidity until it finds a hole, either its own or that of another crab, 

 into which it can dart. If a hole is not available it will take to the water, run out a few feet from the 

 shore and settle into the sand. 



The egg-laying season appears to be confined to the spring or very early summer. The only egg- 

 bearing female we have seen collected was caught in a haul seine near Fort Macon in July, 1913. Only 

 a few unhatched eggs remained of the large number that she had had a few days earlier, for her 

 swimmerets were well covered with empty egg skins. 



