10 
ZOOLOGY OF TIIE VOYAGE OF II.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 denticulated. 
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. 
Ahdomen 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. 
Ahdomen of female ovate, very convex and dilated, five-jointed, the last joint broadly trigonal. 
Hab. Chinese Sea. 
This species comes nearest Naxia 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. ARCTOPSIS STYX. 
Hand multum a Pisa tetraodonte differt, thorace tamen lougiore, et marginibus latero-anterioribus 
crassis spinis in medio armatis ; superiore canthi margine fissura perangusta. 
IIab. Mam-itiuin. 
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 n 243 
t. 17. f. 96; 1 
3. NAXIA, Edwards. 
1. NAXIA DIACANTHA, Be Haan. 
Thorace parte postica lateribus utrimque unispinoso, spina producta, 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. 1 . 
