Rathbun — Neiv Crabs from Gulf of Siam. 11 



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Subfamily HEXAPODIN.E. 



Thaumastoplax orientalis sp. nov. 



Type. — (3^, north of Koh Kut, 10 fathoms. 



Dimensions. — Length, 9 mm. ; width, 12.6 mm. ; width across front and 

 orbits, 5 mm. ; greatest width of front, 2.8 mm. 



Carapace longitudinally very convex, transversely very level; lateral 

 borders marked by a raised line ; antero-lateral margin angularly arcuate, 

 postero-lateral margin.s subparallel; posterior margin convex. Front 

 posteriorly constricted, anterior margin concave, a shallow median 

 tooth. Epistome obsolete in the middle. Propodus of endognath as 

 wide as long. Chelipeds short, stout. Second leg much larger than first 

 and third which are subequal. Third and fourth segments of abdomen 

 fused, also fifth and sixth ; appendages of first segment much longer than 

 the abdomen, but doubly recurved, forming togetlier a figure 8. 



Thaumastoplax chuenensis sp. nov. 



Type. — c?, Koh Chuen, 30 fathoms, shell bottom. 



Dimensions. — Length, 3.6 mm. ; width, 4.8 mm. ; width across front 

 and orbits, 2.5 mm. ; greate.st width of front, 1.5 mm. 



Differs from the preceding in narrower carapace, gastric region sharply 

 outlined; antero-lateral margin less angled, fronto-orbital distance 

 greater, front wider, epistome complete, legs narrower. 



Lambdophallus anfractus sp. nov. 



Type. — (3, off" Koh Kut, 6 fathoms. 



Dimensions. — Length, 4.7 mm. ; width, 7.3 mm. 



Carapace subquadrilateral ; anterior angles rounded; convex in both 

 directions. Front nearly vertical, subtruncate. Orbits oblong-oval. 

 Eyes almost immovable, pigmented. Buccal cavity narrows anteriorly; 

 inner margin of ischium-merus so convex that the space between ischinm- 

 joints is nearly filled by the palpi. First segment of sternum with a 

 transverse sinuous trench for the projecting extremities of the abdominal 

 appendages. Third to fifth segments of abdomen completely fused, sixth 

 segment nearly as long as wide, seventh segment subtriangular with con- 

 vex sides. 



Family XANTHID^. 

 Subfamily MENIPPINM:. 

 Pilumnus borradailei sp. nov. 

 Type. — (3, Koh Chang, 1 fathom, coral. 



Dimensions. — Length, 7.4 mm. ; width, 10 mm. ; fronto-orbital width, 

 7.1 mm. ; width of front, 3.5 mm. 



Carapace flattened; a fringe of long hairs on anterior border; antero- 

 lateral regions a little granular. Lobes of front very oblicjue, convex. 

 Superior orbital fissures small, outer notch broad. Four antero-lateral 

 lobes, gradually diminishing in size. Palms covered with pearly gran- 

 ules; only distal half of fingers is dark colored. Nearest to P. pi7os its 

 Fulton and Grant. 



