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defined by very distinct sulci, and the whole of its upper surface,
except near the posterior margin, very uneven ; the front is deeply
concave in the middle line, and its median interautennnlary portion
much defiexed, spinulose, the spinules of unequal length ; its lateral
margin armed with about seven spinules, and the protogastric lobes
also spinulose ; the peduncles of the antennæ aro without spinules.
The merus-joint of the outer maxillipedes fits into a deep notch in
the anterior margin of the preceding joint, and is itself excavated
at its distal end. The single chelipede present in tho unique example
before me has a spinulose lobe or tooth at the distal end of
the inner margin of the arm ; the Avrist aud palm are flattened on
the upper surfece, v'hich is armed with tubercles arranged in longitudinal
series, the tubercles themselves for the most part minutely
spinulose ; the inner margin of the Avrist is armed AAÙth three or
four spines at its base, and beyond Avith smaller spinules ; the
posterior margin is armed with about seven spines ; there are two
spines at the distal end of the inner margin of the palm, and its
outer margin is spinulose and pubescent ; the fingers meet closely
along their inner margins, which are entire, and their outer margius
are spinulose. The first pair of ambulatory legs have the anterior
margins of the merus, carpus, and propus armed with a few
distant spinules, whieh are almost wholly absent from the same
joints in the following legs. Colour whitish. The single specimen
examined is a female : the carapace measures nearly 3 lines (6 millim.)
in length and 2 | (5 millim.) in breadth ; the chelipede, when
extended as far as its conformation will allow, about 5 lines (11
mOlim.).
The single specimen was ohtained at Port Molle, between tidemarks
(No. 103), Petrolisthes japonicus. The description given
above will show th at our specimen differs from Mr. Haswell’s type
in the more uneven carapace with more numerous lateral marginal
spinules, non-pnhescent posterior margin of the wrist of the chelipede,
and in having two spines (not mentioned by Air. Haswell) at
the distal end of the anterior margin of the palm (see fig. c).
If distinct, I would propose to designate this species P. dorsalis.
I t seems, upon the whole, to have more afiinity with the genus
Petrolisthes than with Porcellana, on which account I refer it,
although with some hesitation, to th at genus.
16. Polyonyx obesulus. ( P l a t e XXIX. fig. D.)
Porcellana ohesula, White, List Crust. Brit. Mus. p. 130 (1847), descript.
nullâ.
I refer to this species, though somewhat doubtfully, a female
ohtained from Port Denison, 4 fms. (No. 122), also one from Prince
of Wales Channel, 7 fms. (No. 169), one from AVest Island, 7 fms.,
and one from Port DarAvin, 12 fms. These examples resemble the
three specimens in the British-Museum collection, and differ from
!
Dana’s description of his P. biunguiculatus *, iu having a distinctly
trilobate front, the middle lobe of which is broad, suhacute, or
rounded, and not much more prominent than the lateral lobes ;
whereas in P. biunguiculatus, to which species specimens from the
Gulf of Suez (B . MacAndreiv) appear to belong, the median lobe is
very prominent and acute and the lateral lobes obsolete. The specimens
referred to P. biunguiculatus also differ from P. obesulus in
having the outer surface of the palms of the chelipedes much more
closely punctulated. The céphalothorax is narrowest in the smallest-
sized specimens ; and in the female from Port Denison (which is
one of the largest examples I have seen) is much broader than in
the others ; but I cannot regard this character by itself as of specific
importance.
I am inclined to doubt whether the genus Polyonyx is distinct
from Megalobrachium. Stimpson merely distinguishes the latter
on account of the absence of the prominent accessory claw, which
gives to the dactyli of the species of Polyonyx a biunguiculate
appearance. The type of 'Megcdohrachium {M. granuUferum, Stm.)
is from the AVest Indies ; but Stimpson refers the P. macrochelis,
Gibbes, from Carolina, to tho genus Polyonyx. The other species of
the latter genus are Oriental in habitat.
Specimens are referred to P. biunguiculatus by Air. HasweU from
Holborn Island, Port Denison, by whom also this species is retained
in the genus Porcellana (vide Cat. p. 147).
17. Pachycheles pulchellus (Haswell). ( P l a t e XXX. fig. A.)
Porcellana pulchella, Hasivell, Proc. Linn. Soc. N. S. Wales, vi. p. 758
(1881) ; “Cat. Austr. Crust, p. 148 (1882).
As Mr. Haswell’s description is very brief, I append the following
from specimens received from Dr. Coppinger :—
The carapace is smooth, rather convex, rounded on the sides, and
hence somewhat orbiculate in outline, faintly striated on the sides
at the back of the branchial regions. The front is rather broad, and
in a dorsal vicAV its margin appears straight ; in an anterior vieAV it
is seen to he bisinuated, with a broadly rounded hut very slightly
prominent median lobe. The orbital and lateral margins of the
carapace are entire. The first exposed joint of the peduncle of the
antennæ is shorter than the following joint, and has sometimes a
small blunt prominence on its inner margin ; the third joint is
short; the flagellum somewhat elongated, with the joints almost
naked. The ischium of the outer maxillipedes has a spine at its
outer distal angle ; the next joint has a prominent lobe on its
inner margin ; the three following joints are robust. The chelipedes
are robust, hut not so broadly dilated as iu most species of this
genus ; the merus or arm is very short ; wrist with broad low prominences
disposed in longitudinal series on its upper surface, and
* Vide U.S. Explor. Exped. xiii., Crust, i, p. 411, pi. xxvi. fig. 1 (1852).
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