864 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Pilumnus tseniola, sp. nov. 
(PI. xi, fig. 3.) 
Carapace very wide, about five-sevenths as long as wide; slightly convex transversely, more con- 
vex in the opposite direction, the anterior half being strongly declivous; in shape oval-oblong, the 
postero-lateral margins being not far from parallel; regions scarcely indicated; surface smooth, punc- 
tate, pubescent and thinly clothed with long fine hair. 
Fronto-orbital width four-fifths width of carapace. Margin of front not visible in dorsal view; 
lobes convex, most produced in their inner half; outer angle small and inconspicuous, as is also the 
inner angle of the orbit. Orbit very oblique, margin granulate, without fissures, a slender sharp spine 
at outer angle; inner lower angle very obtuse, not nearly so advanced as the upper angle. 
Antero-lateral margin convex, only 
half as long as postero-lateral and armed 
with two very small slender spines ad- 
ditional and similar to the orbital and 
quite independent of the general outline 
of the carapace. 
Antennules stout, transversely 
folded, basal joint inflated. 
Antennse with basal joint slender, 
not quite reaching end of lower angle of 
orbit; second joint loose in orbital hia- 
tus; flagellum long, reaching farther 
back than posterior lateral spine. 
Endostomial ridges well defined, 
reaching the anterior boundary of the 
buccal cavern. Outer maxillipeds small, 
not filling the buccal cavity. 
Chelipeds equal in the female (the 
male lacks a right cheliped), short; arm 
granulate outside, a sharp-pointed tooth 
above near distal end, behind it the 
margin slightly roughened; wrist granulate, a long spine at inner angle, with a shorter one below it; 
palm higher than its superior length, upper margin very convex, outer surface granulate. Chelipeds 
and legs clothed with long hairs, which only partially obscure the surface. Hairs and granules con- 
tinued part way on the fingers. Prehensile teeth of pollex larger than those of dactylus. When the 
fingers are closed the tips cross and there is a very slight hiatus at base. 
Legs long and slender; a slender spine at distal end of upper margin of meral and carpal joints; a 
ionger spine at distal third of the same margin of the merus of each pair except the last. 
Abdomen of male with seven separate segments. 
Dimensions.— Female type, length 5.8, width 7.7, fronto-orbital width 6.4 mm. ; male, station 3876, 
length 5.6, width 7.1, fronto-orbital width 6 mm. 
Distribution . — Auau channel, 28 to 43 fathoms, station 3876; Penguin bank, 28 to 14 fathoms, station 
4034 (type locality). Cat. No. of t-ype, 29554. 
In regard to the antennae and maxillipeds this species approaches Platy pilumnus, but the endosto- 
mial ridge clearly reaches the anterior margin of the buccal cavern. The type species of that genus, 
P. gracilipes Alcock, also differs notably in its flat carapace. Our species in its shape approaches P. 
rolumanus Borradaile, which possesses larger anterodateral spines and more elongate chelse. 
The two specimens agree in characteristic color pattern, being ornamented in the anterior half, 
both above and below, by light bands bordered on each side with a narrow stripe of dark brown. 
Pilumnus ovalis A. Milne Edwards. 
Pilumnus ovalis A. Milne Edwards, Ann. Soc. Entom. France, (4), VII, 1867, 280. 
Hawaiian Islands (A. Milne Edwards). 
