10 ZOOLOGY OF THE VOYAGE OE H.M.S. SAMARANG. 



rather slender, subcylindrical, laterally compressed, and covered with long, stout, scattered 

 hairs, claws slightly gaping in the middle, curved inwards, and finely denticidated. 



Second and third pairs of legs one and a half times longer than the carapace, covered 

 with a close, dense, brown tomentum ; third joints subcylindrical, dilated anteriorly ; fourth 

 joint elongately conical. Fourth and fifth pairs of legs shorter than the second and third 

 pairs. Claws sharp, strong, and curved. 



Abdomen of male six-jointed, with a row of prominent tubercles in the middle line, the 

 second joint the widest, with a nipple-shaped tubercle on each side of the central tubercle, 

 the remaining segments becoming gradually narrower, the last being triangular and pointed. 

 Abdomen of female ovate, very convex and dilated, five-jointed, the last joint broadly trigonal. 



Hab. Chinese Sea. 



This species comes nearest Nawia diacantha of De Haan (Tab. 34. Fig. 1), but in that 

 species the frontal spines are very long, straight, and diverging ; the fore-legs very large, thick) 

 and strong ; and the carapace is armed on each side with a stout, strong, and prominent 

 spine ; N. diacantha wants, moreover, the three tubercles on the lateral regions, the form of 

 the carapace is more trigonal, and the legs are much shorter in comparison with the carapace 

 than in Pisa Sinope. 



2. ARCTOPSIS, Lamarck. 



1. AECTOPSIS STYX. 



Haud multum a Pisa tetraodonte differt, thorace tamen longiore, et margmibus latero-anterioribus 

 crassis spinis in medio armatis ; superiore canthi margine fissura perangusta. 

 Hab. Maui'itium. 



Does not differ much from Pisa tetraodon, but the carapace is more elongated, and the 

 latero-anterior margins are armed in the middle with thick spines, while the superior edge of 

 the orbit has a very narrow fissure. 



Hab. Mauritius. 



Pisa Styx, Latr. Enc. Metli. 10. 141. Edw. Crust, vol.i. p. 308; Cancer Styx, Herbst. vol.i. p. 243. 

 t. 17. f. 96 ; 



3. NAXIA, Edwards. 



1. NAXIA DIACANTHA, De Haan. 



Thorace parte postica lateribus utrimque unispinoso, spina product!, fronte bicornuta, cornibus acutis 

 simplicibus, regione ventriculi media unituberculata. 



Lateral margins of the carapace armed at the posterior part with a single spine on each 

 side, spine produced, front with two horns ; horns acute, simple, a single tubercle on the 

 middle of the ventricular region. 



Pisa (Naxia) diacantha, De Haan, Eaun. Japon. t. 24. f. ] . 



