304 



BULLETIN 15 8, UNITED STATES NATIONAL MUSEUM 



by the highly vaulted anal segment. It is much less common than 

 either of the species of Ratlibwtmla^ and like them seems to be con- 

 fined entirely to the beach sands. 



Family PONTOSTRATIOTIDAE 



Genus AEGISTHUS Giesbrecht, 1891 



Body slender ; head separated from the first segment, the forehead 

 produced into a sharp, spinelike rostrum, which is immovable; uro- 

 some less than one-third the length of the metasome ; genital segment 

 divided; abdomen 3-segmented; caudal rami longer than wide, each 

 with a single apical seta twice the length of the body, plumose only 

 at its tip. First antennae 6- or 7-segmented; exopod of second an- 

 tenna 1-segmented ; rami of first four pairs of legs 3-segmented ; fifth 



legs linear and indistinctly 2-seg- 

 mented. Male unknown. One 

 species found here. 



AEGISTHUS MUCRONATUS Giesbrecht 



FiGUBE 182 



Aeffisthus mucronatus Giesbrecht, Fauna 

 und Flora des Golfes von Neapel, vol. 

 19, p. 573, pi. 4G, figs. 46-49, 51; pi. 

 49, figs. 2, 3, 6, 10, 1892. 



Occurrence. — A single female was 

 obtained in a vertical haul at Sta- 

 tion 20069, Grampus, March, 1920, 

 southeast of Georges Bank. 



Distribution. — Tropical Pacific 

 (Giesbrecht) ; Gulf of Guinea (T. 

 Scott) ; coast of Ireland (Pearson) ; 

 North Sea (van Breemen) ; North 

 Atlantic ( F a r r a n, Thompson) ; 

 coast of South Africa (Cleve) ; 

 Malay Archipelago (A, Scott). 

 Color. — Unknown. 

 Female. — Rostrum long narrow and acuminate; dorsal surface of 

 metasome without a network of ridges ; the last four metasome and 

 all the urosome segments fringed on their posterior margins with 

 stout spines ; caudal rami attached to the ventral surface of the anal 

 segment in front of its distal end; apical setae three and one-half 

 times the length of the body. First antennae 6-segmented, the third 

 segment bearing an aesthetask as long as the entire antenna ; endo- 

 pod of second antenna 4-segmented, the two basal segments very 



Figure 182. — Aeyisthus mucronatus; a. 

 Female, dorsal ; b, female, fifth leg 



