294, DR. J. G. DE MAN ON THE PODOPHTHALMOUS 
this singular tooth. The slender carpopodites reach to the 
anterior margin of the cephalothorax, and are a little shorter 
than the meropodites. The propodites are quite half as long as 
the meropodites, and the straight, acute dactylopodites are still - 
a little shorter than the propodites. 
As regards the female of this species, there is the strange fact 
that two of the eight female specimens differ slightly from the 
others by the structure of the last pair of legs and of the 
“ventral plate.” These two specimens, however, completely 
agree in all other characters with the remaining six individuals. 
The fourth pair of legs of the female are as long as in the 
male, reaching as far forwards as the anterior legs; these legs 
also fully resemble the corresponding legs of the male, but their 
meropodites are simple and not enlarged. The fifth pair of 
legs of both females are about as long as those of the male and 
are similar to them, but the meropodites are simple and do not 
present the peculiar notch and the characteristic surmounting 
tooth of the male. In six female specimens, which I shall speak 
of as A, the upper margin of the ischium-joint of the fifth pair 
of legs is dilated into a small, compressed, lamellate, triangular 
crest, broadest posteriorly and gradually tapering towards the 
distal end of the joint. In the two other female specimens 
(B) this crest is wanting, so that the ischiopodite presents the 
same form as in the male. 
The singular organ called by Spence Bate the petasma 
presents a very characteristic form in P. Lysianassa, but so 
difficult to describe that I refer to the figure. The petasma, 
which reaches anteriorly to the bases of the second legs, 
consists of a longitudinal tube which presents a median longi- 
tudinal fissure on the posterior surface; the latter 1s convex 
anteriorly and slightly concave posteriorly. Hach lateral mar- 
gin of the petasma presents a small triangular prominence about 
its middle and directed forwards. At its distal end the petasma 
is armed on each side with two spines or teeth, the proximal 
ot which is very acute, and the anterior surface bears two pairs 
of dentiform prominences, one pair near the base, the other near 
the distal extremity. 
The rami of the uropoda are narrow, ovate, and much longer than 
the terminal postabdominal segment ; they are slightly pubescent 
above, and fringed as usual with hairs along the lateral margins. 
In the male the outer surface of the basal joint of the uropoda 
