648 PROCEEDINGS OF THE NATIONAL MUSEUM vol. iis 



Comparison of the male gonopods of the species of Plagusia in the 

 national collections [P. chahrus (Linnaeus, 1758); P. dentipes (De 

 Haan, 1835); P. depressa; P. glabra Dana, 1852b; P. immaculata 

 Lamarck, 1818; P. speciosa Dana, 1852a; and P. tuherculata Lamarck, 

 1818] indicated that P. depressa, P. immaculata, and P. tuherculata 

 are most closely related to each other (although they are probably 

 specifically distinct) than they are to the other four species. 



Distribution: West Africa and off -lying islands from Senegal to 

 Angola; western Atlantic from South Carolina to Brazil; Bermudas; 

 St. Helena. Littoral and on ships' hulls and other floating objects. 



Family Majidae 

 Subfamily Acanthonychinae 



Acanthonyx sanctaehelenae, new species 



Figures 12, 13e-h 



Material: Off Rupert's Bay; buoy; 0-2 meters; Feb. 2, 1959; 3 

 males, 1 juvenile [1 male is holotype, USNM 112458].— Same; buoy 

 and cable; 0-75 meters; Mar. 18, 1960; 6 males, 1 female.— Same; 

 Apr. 5, 1962; 1 ovigerous female.— Same; buoy; 0-2 meters; Feb. 11, 

 1963; 4 males, 1 ovigerous female. 



Description: Carapace broadly pear shaped in adults; length of 

 males in midlme, not including rostral horns, one-sixth to one-fifth 

 longer than maximum breadth; adult females proportionately broader. 

 Dorsal surface of carapace and legs of large males with very fine but 

 tough pubescence forming tangled mat of long hairs on margins of 

 carapace, chelipeds, and anterior walkmg legs; less dense covering of 

 shorter hairs on most of dorsal surface of carapace and on posterior 

 legs. Hepatic lobe produced anteriorly, not rectangular. Two low, 

 subequal lobes or teeth on branchial margm. Rostral horns and 

 preorbital, hepatic, and branchial lobes bearmg terminal tufts of stout 

 setae. Rostral smus narrowly V-shaped. Basal article of antennae 

 unarmed, two succeeding articles subcylindrical, reaching as far as end 

 of rostral horns. Chelipeds with merus subtriangular, two lobes near 

 proxhnal end of outer margin; carpus with blunt outer crest; chela of 

 male swollen, slightly compressed dorsally; fingers gaping thi'oughout 

 in male, only proximally in female. Abdomen with fourth and fifth 

 somites indistinguishably fused in both sexes, thu'd and f om-th somites 

 partially so in large males, 



Male abdomen and gonopods as figured. 



Measiu-ements: Carapace of male holotype, 18.0 mm. long in mid- 

 line, 20.0 mm. to tip of rostral horn, 15.0 mm. in maximum width. 

 Carapace lengths of male paratypes in midlme, 4.7-16+ mm.; of 



