346 



46 



deflexed, medially sulcate, lower margin arcuate, faintly emarginate in the middle. 

 Orbits almost circular; eyes faintly pigmented. 



Buccal cavity with sides parallel. Antero-external angle of merus of outer 

 maxillipeds well marked but not produced. 



Chelipeds about one and one-half limes as long as carapace. Inner angle of 

 wrist not prominent. Palm pubescent and on the lower half finely granulous. 



Second and third legs subequal. Second pair longest, about twice as long as 

 carapace. 



Neither of the two specimens is adult, and the segments of the abdomen are 

 not clearly marked; save for the broad first segment, the abdomen is very narrow, 

 being at the third segment less than one-third the width of the sternum. 



Length of type c? 2-7 mm., width 3-6 mm., fronto-orbilal width 2 mm., frontal 

 width 09 mm. 



Between Koh Mesan and Cap Liant, 5—8 fath., sand, stones; H. 7 ; 1 c? type. 

 S. of Koh Mak, 5—6 fath.; IL 17; 1 c?. 



Subfamily Hexapodinæ. 

 Thaumastoplax orientalis Rathbun. 



Plate II, iig. 1. 

 Thaumastoplax orientalis Kathbun, Proc. Hiol. Soc. Washington, XXII, 113, 190». 



Carapace one and two-fifths times as broad as long; longitudinally very 

 convex, transversely nearly level; naked and coarsely punctate, a faint H-shaped 

 depression at the middle. Lateral borders marked by a raised line. The fronto- 

 orbital distance, while about two-fifths as great as the extreme width of the carapace, 

 occupies only a little more than half of the anterior margin, 

 the so-called antero-lateral margin being angularly arcuate, its 

 anterior portion transverse, a slight notch on the outer portion, 

 postero-lateral margins sub-parallel ; posterior margin convex, 

 postero-lateral angle obliquely cut off above the insertion of the 

 third leg. 



Front one-fourth the width of the carapace, posteriorly 

 constricted, anterior margin concave, except for a broad shallow 

 median tooth. Orbits transversely oval, appearing marginal in 

 a dorsal view. Antennæ in the orbital hiatus; flagella three 

 times as long as the major diameter of the orbit. 



Epistome obsolete in the middle , narrow at the sides. 



Fig. 33. Thaumastoplax 

 orientalis, type cf, 126 



mm. wide: a, abdomen; jjuccal cavity much broader than long, anteriorly arcuate, sides 

 6, abdominal appendages. .-ij- i,^, -n-ji -iin 



anteriorly divergent. Outer maxillipeds large , especially the 



palpus, which occupies the length of the cavity; a hiatus exists between the palpus 



and the ischium; there is a transverse fringe of hair across the middle of the 



maxillipeds, as well as a marginal fringe on the last two joints. Anterior half of 



