194 SMITHSONIAN misce;llan£;ous collections 



men the central triangular piece is small, while the lateral pieces are 

 very large. The color in life is white, with a few large, blue, mar- 

 ginated spots or ocelli on the hands and the anterior portion of the 

 carapax. Length of the carapax in the male, 0.425; breadth, 0.34;, 

 length of greater hand, 0.59; breadth, 0.2 inch. 



This species is found in considerable numbers hiding between the 

 leaves of the common Pennatula on muddy bottoms in six fathoms, 

 in the bays opposite Hongkong, China. 



Genus POLYONYX Stimpson 



This genus is closely allied to Megalohrachinm in form and gen- 

 eral appearance, but differs in the character of the terminal joints of 

 its feet and its habits. It also resembles Pisosoma, but may be 

 distinguished by the enlargement of the coxal joint of the antennae. 



Carapax rounded-oval, as broad as or broader than long, convex, 

 and smooth. Sides strongly convex and obtuse. Front rather nar- 

 row, straight, and not prominent. Eyes minute. First joint of 

 antennulse not toothed, but flattened or truncate at the outer surface. 

 Coxal joint of antennae as in PorceUana, etc., but very much elon- 

 gated. Chelipeds smooth; meros- joint large. When the chelipeds 

 are folded or retracted the hands do not touch each other. The 

 dactyli of the ambulatory feet are very short and broad, rounded 

 and armed with two or more unguicles on the inner edge. 



The typical species of this genus, P. niacrocheles (Gibbes) ,is known 

 to be parasitic, living in the tubes of large worms. The habits of 

 the other two species, P. biiingulattis and sinensis, are not certainly 

 known, but are probably similar. They inhabit sandy or muddy 

 places, sometimes above low-water mark, but often in water of con- 

 siderable depth. Found in the warm parts of both oceans. 



302. POLYONYX SINENSIS Stimpson 



Plate XIX, Fig. 5 



Pohonv-v sinensis Stimpson, Proc. Acad. Nat. Sci. Phila., x, p. 244 [82], 

 "1858. 



Carapax convex, of a subquadrate form, with the corners rounded ; 

 surface smooth, but faintly striated near the margins. Front rather 

 broad, scarcely perceptibly convex. Chelipeds very unequal, smooth, 

 and glossy ; in the larger one the meros is more than one-half as 

 large as the carpus, and not dilated anteriorly ; carpus almost as long 

 as the hand, with its anterior margin expanded into a laminiform 



