CRUSTACEA OF THE MERGUI ARCHIPELAGO. 61 
acute tooth is present on each side, which is separated from 
the median lobes and from the obtuse, slightly granular, internal 
orbital angles on each side by a small cleft. The orbits have the 
usual size and form; the upper orbital margin presents two 
fissures by which it is divided into three portions, the two external 
of which are covered with a few granules,; whereas the much 
larger internal portion is almost smooth. 
The external orbital angle is little prominent, and not spiniform; 
it is separated by a small hiatus from the inferior orbital angle, 
which is denticulate, being armed with six or seven acute teeth 
besides the also denticulate internal lobe, which projects as much 
forward as the external frontal teeth. The antero-lateral margins 
are shorter than the postero-lateral; they are armed, behind the 
little prominent external orbital angle, with three acute, dark- 
pointed, spiniform teeth. The external margin of the first antero- 
lateral tooth, 2. ¢. the outer orbital angle, is minutely denticulate, 
and the external margin of the second antero-lateral tooth, which 
is spiniform, is also somewhat granular at its base. The external 
margins of the two posterior antero-lateral teeth are quite smooth. 
A subhepatic spine which occurs in so many species of this genus 
is wanting in P. Andersoni, its place being occupied by a small, 
somewhat prominent, acute granule. The postero-lateral margins 
are straight and very slightly concave. The posterior margin of 
the carapace is bordered by an impressed line, running close to 
and parallel with it. The external antenne are long, measuring 
twice the distance of the internal and external angles of the 
orbits, and they reach almost to the penultimate antero-lateral 
spine. When the cephalothorax is viewed from above, the an- 
tennal peduncle is visible in the cleft or hiatus that separates 
the internal orbital angles from the external frontal teeth; its 
basal joint, which scarcely reaches a process of the external 
frontal tooth, is twice as long and nearly twice as broad as the 
next or penultimate joint. The terminal joint projects beyond 
the front, and is scarcely shorter than the second joint. 
The subhepatic and pterygostomian regions of the carapace 
are covered with a short down and with numerous minute 
granules ; those which are found on the anterior portion of the 
subhepatic region are a little larger than the others. The endo- 
stome is distinctly longitudinally ridged. The anterior margin 
of the epistome is granular, the posterior margin, z. e. the anterior 
margin of the buccal cavity, is sharp, and similar to that of 
