446 BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



space between the posterior lobes of the carapace; fourth segment 

 much narrower. Terminal claw of second antenna with a small 

 spine on its inner margin; terminal claw of maxillipeds shutting 

 down between two blunt spines on the basal segment. Total length, 

 6-7.5 mm. 



Male. — Carapace more than twice the width of the rest of the 

 body, its lateral areas with a dividing groove between the head and 

 first segment. Plates on the fourth segment smaller than those on 

 the fused second-third segment; terminal claws of second antenna 

 projecting well in front of the carapace. Basal exopod segment of 

 first leg swollen and armed on its outer margin with stout spines 

 curved distally, spine at the outer corner pectinate ; outer margin of 

 terminal segment lobed proximally, its spines pectinate. Total 

 length, 4.5-5.5 mm. 



Reiiiarhs. — Any sunfish captured in the present area will probably 

 yield on its gills, fins, and outer skin specimens of the three genera 

 last described. Sometimes 100 or more may be found on the same 

 fish, whose slow movements and general lethargy seem well suited 

 for parasitism. 



Family ANTHOSOMIDAE 



Genus ANTHOSOMA Leach, 1816 



Female. — Body short and stout, head fused with first segment, 

 carapace ovate, more than half the entire length; genital segment 

 and abdomen covered dorsally by the fourth segment plates and 

 ventrally by three pairs of overlapping foliaceous legs; fourth pair 

 of legs obsolete, the first three pairs without rami. Abdomen 1-seg- 

 mented; caudal rami narrow and elongated and unarmed; first 

 antennae 6-segmented; second antennae 3-segmented, subchelate; 

 maxillipeds uncinate. 



Male. — No dorsal plates on fourth segment ; first two pairs of legs 

 with 1-segmented rami in notches on their inner margins ; third legs 

 without rami; fourth legs obsolete; other appendages as in the 

 female. A single species in this area. 



ANTHOSOMA CRASSUM (Abildgaard) 



FlGtTRE 281 



Caligus crassus Abildgaaed, Skrivt. Naturh. Selsk., vol. 3, p. 46, pi. 5, 1794. 

 Anthosoma crassum Wilson, Proc. U. S. Nat. Mus., vol. 60, art. 5, p. 23, pi. 1, 

 1922. 



Occurrence. — Found on the gills of the common sand shark, the 

 porbeagle shark {Isunis pimctatus), the sharp-nosed mackerel shark 

 (I sums tigrls), and the jaw of the dusky shark, captured in the 

 fish nets on Marthas Vineyard. 



