CRUSTACEA OF THE MERGUL ARCHIPELAGO. 291 
as, e. g., the dorsal median ridge, a lateral longitudinal ridge 
proceeding from the hepatic spine to the posterior margin, the 
posterior margin itself, &c., so that the pubescence appears 
only on those parts of the outer surface which are slightly 1m- 
pressed. 
The rostrum is very short, and reaches only halfway to the 
end of the eye-peduncles; it is strongly laterally compressed, 
tolerably high, and the lateral surfaces are pubescent. The 
upper margin of the rostrum is slightly declivous towards the tip, 
which is acute; it is armed above with six small acute teeth, 
which gradually decrease in size towards the tip. These six teeth 
are about equidistant ; the anterior tooth is placed close to the tip, 
and the three posterior ones are situated on the dorsal surface of 
the carapace, the fourth being placed precisely above the frontal 
margin; the upper margins of these six teeth are microscopically 
crenulate and fringed with short hairs. They are preceded 
by a seventh small acute tooth found at the base of the 
rostrum, a little before the middle of the cephalothorax. The 
slightly ascending lower margin of the rostrum is entire and 
unarmed. The rostrum is continued backwards into a smooth, 
glabrous, blunt, scarcely elevated ridge, which divides imme- 
diately before the posterior margin of the carapace into two ridges, 
which proceed towards the postericr margin. In P. Richtersii 
the two posterior teeth of the rostrum are situated on the dorsal 
surface of the carapace. by 
The anterior margin of the cephalothorax is armed with an 
acute antennal spine and with a small supraoccular tooth; there 
is also a small hepatic spine. The antennal and hepatic grooves 
are scarcely indicated; but the gastro-hepatic sulcus, which pro- 
ceeds from the hepatic spine obliquely upwards and backwards 
towards the middle of the dorsal median ridge of the carapace, 
is distinctly marked. The antero-inferior angle of the cephalo- 
thorax is not toothed. The eye-peduncles are very short, and 
scarcely reach to the distal end of the antepenultimate joint of 
the antennulary peduncles ; the latter are a little shorter than 
the antennal scales. In nearly all these specimens the flagella of, 
the internal antenne are unfortunately broken off; in a single 
specimen only are they still partly preserved. These flagella 
are, as L suppose, about as long as their peduncles ; the outer or 
upper one is much thicker than the other, but it soon tapers 
a little beyond the tips of the antennal scales. The peduncles of 
ioe 
