246 
THE VOYAGE OF H.M.S. CHALLENGER. 
Gonoplax sinuatifrons, n. sp. (PL XX. fig. 2). 
The carapace is shaped nearly as in Gonoplax rhomboides (Linne), i.e., it is 
moderately convex in a longitudinal direction, transverse, with the antero -lateral angles 
prominent and spiniform, the lateral margins slightly tumid at the hepatic regions, and 
thence slightly convergent to the postero-lateral angles; the dorsal surface is smooth and 
glabrous. The front is rather less than one-third the width of the carapace, its anterior 
margin not straight, as in Gonoplax rhomboides, but with a wide, shallow, median sinus; 
the lateral angles are rounded. The upper and lower orbital margins are undulated nearly 
as in Gonoplax rhomboides, which this species closely resembles also in the form of the 
ocular peduncles, antennae, and outer maxillipedes. Chelipedes, in the small female, of 
moderate length; merus with a small tooth near the middle of its upper margin, as in 
Gonoplax rhomboides, and with another on the inferior margin ; carpus with a tooth on 
its inner margin, but with the small tooth of the outer surface (present in Gonoplax 
rhomboides) nearly obsolete ; chela less elongated than in Gonoplax rhomboides, and 
deeper in proportion to its length ; the palm is rounded above and carinated below as in 
the European species, and the fingers somewhat more robust. The ambulatory legs as 
in Gonoplax rhomboides. Colour (in spirit) yellowish brown. 
Young J . 
Lines. 
Millims. 
Length of carapace, rather over . 
3 
7 
Breadth of carapace, .... 
H 
9-5 
Length of a chelipede, .... 
61 
13-5 
Length of second ambulatory leg, 
8J 
18-5 
The unique specimen (a female, probably not fully grown) was dredged at Amboyna, 
in 15 to 25 fathoms. 
This specimen is only distinguishable from the well-known European Gonoplax 
rhomboides by slight differences in the form of the front and chelipedes, which are 
referred to above, but probably additional specific characters would be derived from 
adult male examples. 
Ommatocarcinus, White. 
Ommatocardnus, White, Append, in Stanley, Voy. H.M.S. “Rattlesnake,” vol. ii. p. 393, pi. v. 
fig. 1, 1852. 
„ Milne Edwards, Ann. d. Sci. Nat., ser. 3, Zool., vol. xviii. p. 163, 1852. 
Carapace transverse, longitudinally rather convex, with the dorsal surface smooth, 
the sides converging slightly to the posterior margins ; the antero-lateral angles pro- 
longed as long spines. The front is very narrow, less than one-sixth the anterior 
width of the carapace in the adult male, it is deflexed, and constricted between the bases 
of the eye-peduncles as in Macrophthalmus. The epistoma is linear-transverse. The 
