112 Rathbun — New Crabs from Gulf of Siam. 



AnU'rior border of carapace, chelipeds and legs fringed with long hair. 

 Four lateral teeth, of which the third is triangular and prominent. Arm 

 with a thin crest above, forming a tooth near end of segment; wrist 

 eroded; fingers long, cylindrical. Legs with a tliin smooth crest on 

 merus, anterior in first three pairs, posterior in fourth pair. 



Subfamily RHIZOPIN.E. 

 Megaesthesius* gen. nov. 



Allied to Camatopsis Alcock. Eyes unpigmented; movable part of 

 antennules immensely stout ; buccal cavern anteriorly narrowed and arcu- 

 ate, outer maxillipeds closing tlie cavity; ischiognath as broad as long 

 and broader than merognath, which is subtriangular and bears the palp 

 at its summit; exognath short and narrow. 



Type and only species, 



Megaesthesius sagedae sp. nov. 



Type. — c?, Singapore, 2-3 fathoms. 



Dimensions. — Length, 2.7 mm. ; width, 2.7 mm. ; frontal-orbital width, 

 1.8 mm. ; width of front, O.fi mm. 



Carapace pentagonal; postero-lateral borders long, parallel; antero- 

 lateral borders short, in line with orbits; front bilobed, lobes arcuate. 

 Antennae slender, crowded by the antennules away from the front. Cheli- 

 peds shorter than legs; palm spinulous below; fingers cylindrical, longer 

 than palm. Legs long, narrow, margins spinulous. Third to fifth seg- 

 ments of abdomen fused. 



Subfamily TYPHLOCARCINOPSIN.E nov. 

 Characters of 



Typhlocarcinops gen. nov. 



Differs from Typhlocareinus Stimpson chiefly in luning the first seg- 

 ment of the male abdomen very broad, covering the whole width of the 

 sternum, and transversely grooved. Remainder of abdomen narrow. 



Type and only species, 



Typhlocarcinops canaliculata sp. nov. 



Typi,'. — cf, between Koh Mesan and Cap Liant, 5-8 fathoms, sand, 

 stones. 



Dimensions. — Length, 2.7 mm. ; width, 3.6 mni. ; fronto-orbital width, 

 2 mm. ; frontal width, 0.9 mm. 



Carapace widest posteriorly, lateral margins granulate, entire. Front 

 widening anteriorly, strongly deflexed, lower margin annate and faintly 

 emarginate. Orbits circular, eyes slightly pigmented. Buccal cavity 

 with siiles parallel; antero-external angle of merognath not produced. 

 Chelipeds about 13^ times as long as carapace; second and third legs sub- 

 equal, second longest. 



*lj.iyas, great; aio-drjais, perception by feeling. 



