290 DR. J. G. DE MAN ON THE PODOPHTHALMOUS 
their carpopodites are scarcely twice as long as the depressed 
lanceolate dactylopodites. The last legs are nearly as long as 
and similar to those of the fourth pair. 
The rami of the uropoda are much longer than the terminal 
segment of the postabdomen, and are quite similar to those of 
P. semisulcatus. 
The largest specimen is about 20 centim. long from tip of 
rostrum to the end of the terminal segment of the post- 
abdomen. 
P. merguiensis differs from P. semisulcatus, de Haan, (1) by 
the form and structure of the rostrum; (2) by the postrostral 
ridge not proceeding backwards to the posterior margin of the 
carapace, and being much less distinctly sulcate; (8) by the 
faintly defined antennal and hepatic sulcus; (4) by the absence 
of the horizontal crest on the antero-lateral surface of the cephalo- 
thorax, which in P. semisulcatus is found below and parallel to 
the hepatic crest, being directed towards the peduncle of the 
outer antenne ; (5) by the inner flagellum of the upper antennz 
being shorter than the external one. P. merguiensis also differs 
from the Australian P. esculentus, Hasw., by its straight rostrum, 
which is armed with more teeth, by the faintly defined gastro- 
hepatic sulcus, and at first sight by the much longer internal 
antenne. It also differs from the still imperfectly known 
P. indicus, with which P. carinatus, Dana, is probably identical, 
by the shape of its rostrum; by the somewhat shorter flagella 
of the internal antenne, of which the external one seems not to 
be dilated at base; by the much shorter flagella of the external — 
antenne ; by the form of the ventral plate ; and probably by some 
other characters. 
161. Penzvus Lystanassa*, n. sp. (PL XIX. fig. 1.) 
Fourteen specimens (63, 82 ) of this interesting new species 
were collected in the Mergui Archipelago. 
Peneus Lysianassa belongs to that group of species in which 
the rostrum is shorter than the eyes ; and it is apparently closely 
allied to P. Richtersii, Miers, from the seas of Madagascar. 
The cephalothorax is scarcely more than twice as long as 
broad, and is scantily clothed with a short pubescence; some 
parts of the surface that are slightly elevated are quite glabrous, 
* Lysianassa, one of the Sea-nymphs. 
