630 PROCEEDINOS OF THE NATIONAL MUSEUM. vol.39. 



Fourth legs with a stout basal joint fully as long as the three ter- 

 minal joints, each of the second and third joints tipped with a short 

 claw, the terminal joint tipped with tlu-ee claws, the inner of which 

 is three times the length of the others. 



Total length, 9.4 mm. Carapace 3.2 mm. long, 3.6 mm. wide. 

 Free segment 0.8 mm. long, 0.6 mm. wide. Genital segment 3.2 mm. 

 long, 1.8 mm. wide. Abdomen 3.2 mm. long, 0.6 mm. wide. 



Male. — Carapace and free segment like those of the female and 

 almost exactly the same size, but the posterior body is shorter and 

 narrower. 



Genital segment spmdle-shaped, only a little longer than the free 

 segment and about the same width; abdomen one-fifth longer than 

 the genital segment and only two-thirds as wide, two-jointed, the 

 basal joint less than half the length of the terminal. Anal laminae 

 fully as large as those of the female and armed with longer spmes, 

 which, however, are nonplumose. 



Second antennse much inflated and covered on the ventral surface 

 with corrugated pads, the terminal claw stout, and reinforced by 

 several accessory claws. Basal joint of fourth legs much smaller 

 than in the female; fifth legs not visible in dorsal view; other append- 

 ages as in the female. 



Total length 6.8 mm. Carapace 3.2 mm. long, 3.4 mm. wide. 

 Free segment 0.8 mm. long, 0.6 mm. wide. Genital segment 1.2 mm. 

 long, 0.8 mm. wide. Abdomen 1.3 mm. long, 0.6 mm. wide. Color a 

 light sulphur yellow, deepening mto orange in the thicker portions 

 of the carapace and the genital segment; eggs yellow. 



A fme lot of specimens numbering twenty females and' six males 

 was obtained from the mouth of a shark caught in Chesapeake Bay, 

 and belong to the museum of the Johns Hopldns University. These ; 

 are cotypes of the new species, and from them two females and a male \ 

 have been selected as types and deposited in the National Museum, 

 under the Cat. No. 39553, U.S.N.M. : 



This new genus belongs to the Euryphorinse and is closely related , 

 to Alebion, but differs from it in having fully developed fourth legs, 

 in the presence of a pair of maxillary hooks and a furca, and in the 

 absence of the enlarged corneous claws on the first three pairs of 

 swimming legs. 



ACKTHEINUS DENTATUS.a new species. 



Female. — Carapace slightly obovate, "v^'idest anteriorly; frontal 

 plates projecting nearly their width, but thorougldy fused with the 

 carapace, their anterior margin evenly rounded, with a slight incision 

 at the center. Sides of carapace and posterior margin quite convex, ; 

 the latter with a deep incision on either side where the lateral area 

 joins the thoracic. Lateral areas wide but curved over ventrally so as 



o Dentalus, toothed, in allusion to the teeth on the second antennae. 



