SHRIMPS FROM THE MARSHALL ISLANDS — CHACE 3 



ever, the pronounced excavation of the posterior margin of the 

 pleuron of the fifth abdominal somite (fig. 2,6) which appears to be 

 characteristic of the species. 



These specimens have the unarmed antennal angle, notched dorsal 

 carina of the second abdominal somite, spinose basis and ischium of 



a 

 Figure 1. — Petasma of Metapenaeopsis sp.?: a, Posterior view, X 7; b, anterior view, X 7. 



the first chelipeds, and the typical dorsal armature of the carapace 

 characteristic of Division I or carinata group diagnosed by Burkenroad 

 (1934, p. 71) and later abandoned by that author (1945, p. 3). Unlike 

 many of the members of that group, however, the present specimens 



a b 



Figure 2. — Sicyonia hispinosa (de Haan)?: a, Thelycum, X 8.2; b, abdomen, X 7.6. 



have the fifth abdominal somite terminating dorsally in a distinct 

 tooth on each side. 



Although it is probable that the Rongelap specimens are con- 

 specific with the young male from the Sulu Archipelago that de Man 

 called S. hispinosa, additional study of Japanese material must be 

 made before they ca.n certainlv be assigned to de Haan's species. 



