DECAPOD CRUSTACEANS OF THE BEAUFORT, N. C, REGION. 447 



Chelipeds moderately stout; hand about one and one-half times as long as wide, fingers gaping at 

 base and of nearly equal length, the immovable one curved upward and with a tooth near its tip; the 

 movable one curved and with a tooth near the middle . Walking legs smooth above and below , pubescent 

 only on the basal articles, the meral and carpal articles more or less crested and fringed with hairs; 

 penultimate pair large and thick. 



Measurements of a male: Length of carapace, 5.2 mm.; width, 10.5 mm.; hand, 4 mm. 



This species, like the others of the genus, is found most frequently as a commensal in some worm 

 tube. An occasional specimen has been found swimming about in the water. 



Family GRAPSIDAE. 



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

 the eyestalks of moderate length, and a gap of at least appreciable size between the 

 third maxillipeds. 



Thirty-nine genera are included in this family. Of these, five are represented in 

 the Beaufort fauna. 



KEY TO THB genera of THE BEAUFORT REGION. 



a. Antennae covered by the front. 



b. Third maxillipeds without a pubescent oblique ridge. 



c. Carapace decidedly broader than long Pachygrapsus. 



cc. Carapace about as long as broad ; legs strongly fringed with hairs Planes. 



bb. Third maxillipeds with an oblique pubescent ridge crossing the ischium and meros Sesarma. 



aa. Antennas visible from above. 



6. Antennules covered by the front; carapace broadest anteriorly Euchirograpstis. 



bb. Anteimules folded back into a pair of deep frontal notches; carapace broadest at about the 

 middle Plagusia. 



Genus PACHYGRAPSUS Randall. 



Pachygrapsus Randall, 1839, p. 127. 



Pachygrapsus transversus Gibbes. Mottled shore crab. PI. xxxvi, fig. 9. 



Pachygrapsus transversus Gibbes, 1850, p. 181; Ratfabun, 1901, p. 17. 



Carapace rectangular, about one-fourth wider than long, depressed, polished, and finely plicate, 

 the plicae being transverse except on the branchial regions, where they are oblique. Sides strongly 

 converging posteriorly and with a well-marked tooth behind the orbital angle. Front slightly more 

 than half as wide as carapace, its edge sinuous, and its upper surface with four low elevations. 



Chela finely granulate, ridged longitudinally on lower outer surface, margins rounded; dactyl with 

 smooth upper margin. Posterodistal angle of the meros of ambulatory legs and anterodistal angle of 

 meros of chelipeds dentate. 



Measurements of a male : Length, 11 mm.; width, 14 mm. 



The ground color is almost black, crossed by numerous fine greenish-gray lines which follow the 

 transverse and oblique plicae and at intervals unite to form spots of various sizes and shapes. The 

 ambulatory legs are dark brown or blackish with gray spots. 



This crab appears to occur in this region very irregularly. The first specimen was collected in 

 1902 from the piles of the railroad wharf at Morehead City. No more were observed until 1912, when 

 it became common on the beaches of Bogue and Shackleford Banks. In 1913 and 1914 it was not col- 

 lected, but in 1915 and 1916 it was again found in small numbers on the Shackleford jetties. Owing 

 to its close resemblance both in appearance and habits to Sesarma cinerea it is apt to be overlooked 

 except by one familiar with it. 



