262 Hyas serrdtus. 



[We have prefixed, rather than appended, the communi- 

 cation on the Pontophilus trispinosus Hailstone, to preserve 

 the order of time. We place next in order Mr. Hailstone's 

 descriptions of the two crabs.] 



Orel. Brachyura, Fara. ikfaiadae, Gen. Hyas, Sp. [? coarctata, in a young 

 state] serratus Hailstone, (fig. 26.) 



a, The external foot-jaw, magnified; .6, the abdomen, magnified. 



Description. — A male. External antenna distant ; the first 

 joint larger than the second, and dilated externally, its outer 

 margin serrrated with 5 or 6 teeth ; the second joint nearly 

 the length of the first, with one prominent tooth, or spine, on 

 its apex at its outer side, and several obsolete ones behind ; 

 apices (tips) of the remaining joints with strong hairs or 

 bristles. — External double palpi (a) with the first joint 

 of their internal peduncle dilated internally, notched at its 

 external apex for the reception of the second joint, which is 

 emarginate at the internal apex. — Shell elongated, tubercu- 

 lated, rounded at the posterior extremity, slightly convex, 

 rostrated in front ; the rostrum fissured, its segments divari- 

 cating, but approximating at their termination, their outer 

 margins serrated, their inner ones obsoletely so. The sides 

 behind the eyes, with a spear-shaped process, its margin 

 serrated ; the orbits of the eyes obsoletely serrated above and 

 beneath, where the surrounding part of the shell is rough with 

 short spines. Bristly. — Eyes not thicker than their pedun- 

 cles. Each peduncle is furnished with three spines; one 

 irregularly cloven, placed at its termination, immediately upon 

 the eye ; one at the anterior side of the peduncle, midway ; and 

 another a little below, nearer the orbit of the eye. — Abdomen 

 (b) 7-jointed, carinate and emarginate ; the first six joints of 

 about equal length ; the first joint broad, the second narrower, 

 the third and fourth somewhat broader, the fifth narrowest, 

 the sixth rather broader, the seventh subtriangular ; the apex 

 rounded ; the first six joints somewhat arcuate at their pos- 

 terior margins ; the posterior corners produced, in the sixth 



