Boone, Crustacea, Cruises of "Eagle" and "Ara," 1921-28 143 



ous spines and with a tuft or brush, of setae on its upper face, serves 

 to distinguish it from all other members of the genus. 



Type: Collected on the coasts of Brazil by a Mr. Olfers, and de- 

 posited in the Berlin Museum. 



Material examined : One specimen taken in a fresh water stream 

 emptying into Chatham Bay, Cocos Island, Pacific Ocean, March 5, 

 1926, by the ''Ara," 



Color: According to the color-plate made by Mr. Belanske, the 

 pair of large chelipeds are deep gentian blue with a purplish cast; 

 the body and other appendages are mottled reddish-brown, the tips of 

 the antennae and pleopoda being yellowish. The plate has been pub- 

 lished by Mr. Vanderbilt, in his "To the Galapagos on the 'Ara'." 



Technical description: Carapace exclusive of rostrum equal to 

 two-fifths of entire body length. Abdomen tapering, convex, laterally 

 compressed. Rostrum short, extending about as far forward as the 

 antennular peduncle and continued backward on the carapace two- 

 fifths of its length, tip acute, upper margin armed with 16 spines, 

 acute, forward-directed, with 8 to 12 stiff, upstanding bristles on the 

 proximal upper margin of each spine. The tip of the spine is trans- 

 lucent, horn-color. There are 2 similar spines on the inferior rostral 

 margin. There is a median longitudinal carina on the lateral face of 

 the rostrum, which carina is posteriorly continuous with the concave 

 ocular margin. The antennal spine is conical, short, acute. Behind 

 and slightly below it on the carapace is another smaller spine. The 

 surface of the carapace is smooth, dotted with numerous coarse punctae, 

 a single depression, scarcely a groove, occurs on each side, just below 

 the antennal spine, and extends backward two-fifths the length of the 

 carapace. The lower lateral parts of the carapace are closely ap- 

 pressed to the underside of the body, the lateral margin carinate. 



The first abdominal segment is only two-thirds as long in the 

 median line as the second segment, and has its lateral margin 

 rounded and posteriorly concealed by the overlapping of the second 

 segment, which laterally is produced into a large, subcircular plate 

 which posteriorly overlaps the third segment; the third segment is 

 as long as the second and has its lateral margin rounded but not 

 produced ; the fourth and fifth segments are subequal, each two-thirds 

 as long in the median line as the third segment and with the posterior 

 margin notched in the upper lateral region, and thence obliquely 

 produced to the postlateral angle which is nearly right-angled, 

 slightly rounded ; the sixth segment is one and one-half times as long 



