REPORT ON THE BRACHYURA. 
227 
Piiumnoplax vestitci (de Haan). Japan; North and North-East Australia (var. 
sexdentata, Haswell). 
Piiumnoplax heterochir (Studer). Off Cape of Good Hope and Agulhas Bank 
(to 150 fathoms); Nightingale Island, Tristan da Cunlia (100 fathoms). 
Piiumnoplax abyssicola, n. sp. Fiji Islands (315 fathoms). 
The nearest ally to this genus is perhaps Pseud orhombila, Milne Edwards, of which 
I formerly regarded Piiumnoplax a subgenus, 1 but the species of Piiumnoplax may be 
distinguished by their much smaller size, and by the narrower basal antennal joint and 
compressed and ciliated dactyli of the ambulatory legs. From the species of Pilumnus, 
and, I think, Pucrate, de Haan, Piiumnoplax is distinguished by the less convex carapace 
with shorter antero-lateral margins, and more slender, longer ambulatory legs, not to 
mention other more important but generally less constant characters. 2 
Piiumnoplax heterochir (Studer) (PI. XIX. fig. 1). 
Pilumnus heterochir , Studer, Abhandl. d. k. Akad. d. Wiss. Berlin, Abh. ii. p. 11, pi. i. 
fig. 3, 1882. 
Pseudorliomhila ( Piiumnoplax ) normanni, Miers, Narr. Chalk Exp., vol. i. pt. ii. p. 587, 
1880. 
The carapace is little broader than long, somewhat depressed, and granulated near 
the front and antero-lateral margins, and with short, obscurely defined, transverse ridges 
on the gastric region and on the front of the branchial regions. The antero-lateral 
margins are much shorter than the postero-lateral margins, which are straight and 
converge to the postero-lateral angles, and the former are divided into three teeth, of 
which the first is broad and obtuse, and the second and third dentiform and acute ; 
behind these, on the postero-lateral margins, there is usually a small tuberculiform 
rudiment of a fourth tooth. The interorbital frontal carina is entire or slightly notched 
in the middle line and granulated ; the frontal margin is divided into two lobes by a 
shallow, triangulate median notch. The orbit has two small notches in its superior 
margin, but none at its exterior angle or on its inferior margin. The third segment of 
the post-abdomen in the male is the broadest, and laterally angulated ; the sixth segment 
is slightly longer than the fifth, the seventh segment slightly transverse and distally 
rounded. The eyes are of moderate size. The basal antennal joint is short and slender, 
and does not attain the lateral subfrontal process. The merus of the outer maxillipedes 
is shorter than the ischium-joint, distally truncated, with a rather prominent antero-external 
angle. The chelipedes (in the male) are unequal, the right usually the larger ; the 
1 Crust, in Bep. Zool. Coll. H.M.S. “Alert,” p. 241 , 1884 . 
2 As has been noted under Pilumnus, the European species described by Maitland as Pilumnus tridentatus, may 
belong to Piiumnoplax or to Heteroplax, which latter genus is, according to Dr. Stimpson’s diagnosis, separated from 
Piiumnoplax by characters of scarcely more than subgeneric value. Besides the species mentioned by Dr. Stimpson, I 
have described one, Heteroplax (?) nitidus , from the Corean Seas. 
