CRUSTACEA OF THE MERGUI ARCHIPELAGO. 281 
from the Sandwich Islands is a distinct species, then the 
Mergui specimens should certainly be referred to Stimpson’s 
P, boninensis. . 
The largest specimen, a male, is 85 millim. long from the tip 
of the rostrum to the end of the terminal postabdominal segment. 
In this specimen the carapace is a little rough anteriorly, being 
covered with minute spinules, arranged irregularly and only 
visible with a magnifying-glass; on the posterior half of the 
cephalothorax these spinules are not found, the upper surface being 
only minutely punctate. In the other younger specimens these 
minute spinules are much less numerous, being still only 
observed on the antero-lateral parts of the carapace, or they are 
even quite absent, the cephalothorax then being smooth. 
The rostrum is characteristic. It is quite similar to that of 
P. superbus, Heller (Novara-Reise, Taf. x. fig. 10), but in this 
species it is generally shorter than the antennal scales and not 
longer. In most specimens, as, indeed, in the largest, the rostrum 
does not reach to the end of the antennal scales, being a little 
shorter than these appendages, but it exceeds the peduncles of the 
internal antenne: in the smallest individual, which is only 40 
millim. long, the rostrum is even a little longer than the antennal 
scales ; whereas in the specimen from Elphinstone Island it is only 
just as long as the peduncles of the internal antenne. In most 
specimens it is a little convex above the eyes and slightly directed 
downwards at the distal end, sometimes, however, it is a little 
curved upwards towards the latter. The rostrum is = toothed ; 
in the largest specimen the formula is a in four other specimens 
= and in the specimen from Elphinstone Island the rostrum is = 
dentate. In the specimens which were collected by Dana at 
the Sandwich Islands the formula was a, but this difference 
may be regarded at most as indicating a local variety. The 
teeth of the upper margin are small and nearly equidistant; the 
first four teeth are placed on the carapace behind its anterior 
margin, the first tooth is found at a distance of a third of the 
length of the cephalothorax from its anterior margin and the 
teeth occur quite to the tip of the rostrum. (In Dana’s figure 
1a six teeth are shown as occurring behind the anterioz 
margin of the carapace; but this figure is certainly incorrect, 
twenty teeth having been figured on the upper margin.) 
The external maxillipeds are of moderate length, being only 
