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THE VOYAGE OF H.M.S. CHALLENGER. 
margins, and are armed with three or four teeth, which are rarely as spinuliform as in 
Pilumnus, to which this genus is somewhat nearly allied. The front is of moderate 
width, slightly deflexed, and distally truncated, and often has a small median notch in 
the anterior margin. The orbits are of moderate size, and their margins are sometimes 
notched, but not spinuliferous. The epistoma is very narrow and transverse. The 
ridges of the endostome or palate are very obscurely defined. The post-abdomen in the 
male is distinctly seven-jointed, and is broadest at the base, where it covers the whole, 
or nearly the whole, width of the sternum, between the bases of the fifth ambulatory legs. 
The eyes are set upon rather short, stout pedicels. The antennules are transversely or 
somewhat obliquely plicated. The basal antennal joint is short and rather slender, and 
usually does not reach the infero-lateral process of the front; the flagellum arises from 
within the interior orbital hiatus. The exterior maxillipedes are closely applied to the 
buccal cavity; their ischium and merus-joints are distally truncated, the merus shorter 
than the ischium, and bearing the next joint at its antero-internal angle, which is very 
slightly, if at all, emarginated. The chelipefles are either subequal or unequal in the 
male, and if unequal, the palms may be dissimilarly tuberculated; the merus-joint of the 
larger chelipede is trigonous, and prolonged little, if at all, beyond the antero -lateral 
margins of the carapace ; the carpus has a spine on its antero-internal margin ; the palm 
is compressed, rounded above, and tuberculated or smooth on the exterior surface; the 
fingers are distally acute and denticulated on the inner margins. Ambulatory legs 
moderately elongated, with the joints slender and unarmed; the dactyli usually styliform, 
but slightly compressed, and ciliated on the margins. 
The species are all of small size, and inhabit the Chinese, Japanese, and Australian 
Seas, in water of moderate depth. Pilumnoplax heterochir, Studer, is a deep-water 
species occurring in the Challenger collection, near the Cape of Good Hope, on the 
Agulhas Bank and at Nightingale Island (Tristan da Cunha group), in 100 to 150 fathoms; 
and I have described a variety ( atlantica ) of the Oriental Pilumnoplax sulcatifrons, 
Stimpson, from Senegambia (Goree Island). In the Challenger collection is another deep- 
water species, Pilumnoplax abyssicola, n. sp., from the Fiji Islands (315 fathoms). 
The following is, I believe, a complete list of the species which have been assigned 
to this genus, but not improbably some others which have been referred to allied genera 
may hereafter be included in it : — 
Pilumnoplax sulcatifrons, Stimpson. Hong Kong ; Port Molle, North-East 
Australia (var. australiensis, Miers), and Goree Island, Senegambia (var. 
atlantica, Miers). 
Pilumnoplax longipes, Stimpson. Oosima, Japan. 
Pilumnoplax sculpta, Stimpson. Oosima, Japan. 
Pilumnoplax ciliata, Stimpson. Limoda, Japan. 
