Boone, Crustacea, Cruise of ''Alva," 1931 185 



Genus: PLAGUSIA Latreille. 

 Plagusia speciosa Dana. 



Plates 95 and 96. 



Type: Dana's type was a beach worn carapace from Waterland 

 Island, Paumotu Archipelago, deposited in the Philadelphia Academy 

 of Sciences. 



Distribution: "Waterland Island, Paumotus, (Dana), recited by 

 de Man, Miers and Ortmann) ; Makemo Island, Paumotus, (Rathbun) ; 

 Tahiti, Society Islands, (Kingsley; Boone) ; Hao Island, Mergui, (No- 

 bili) ; Funafuti Atoll, Rotuma, (Borradaile). 



Material examined : One female, taken on Venus Point Reef, Ta- 

 hiti, Society Islands, August 15, 1931, by the ''Alva." This is an ex- 

 ceptionally fine specimen of this very rare species. 



Color: The preserved specimen which has been in alcohol about 

 two years, has a creamy ground color with a large crimson shield on 

 the gastric-cardiac region, two large crimson spots on each side, one 

 being on the hepatic region and the other on the outer lateral margin. 

 The ambulatory legs are alternately banded with crimson and cream. 



Technical description : The carapace is subcircular, seven-eighths 

 as long as wide, decidedly convex in both directions ; the entire dorsal 

 surface covered with very beautiful squamae ; the regions clearly de- 

 lineated. The frontal margin is deflected, rather broadly triangulate, 

 with a blunt, bifid tip; the margin carinate; this carina continuous 

 with that of the preorbital tooth. The dorsal surface is traversed by a 

 median groove and there are a pair of prominent curved squamae, one 

 on either side of the sulcus, where the frontal margin bends downward. 

 The antennal septum is deep cut, triangulate, situated on either side 

 of the frontal margin, the deep-cut apex of the septum extending up- 

 ward on the dorsal surface and forming the sulcus between the frontal 

 margin and preorbital angle. The latter is triangulate, about two- 

 thirds as wide basally as one-half of the frontal margin, similarly de- 

 flected with carinate margin, emphasized at the outer subdistal side by 

 a squama. The orbital margin is subcircular, unbroken, the postorbital 

 angle is an acute, unbroken spine. There are two additional, slightly 

 smaller, similar spines, one behind the preorbital spine, on each lateral 

 margin. The inferior orbital margin is laminate, slightly denticulate 

 at the inner angle and together with the rather prominent laminate 

 epistome, forms a distinct linear margin to the face. Below the orbital 

 margin the excurrent channel is sharply defined as a ridge, fringed by 



