CRUSTACEA OF THE MERGUI ARCHIPELAGO. 97 
_ informed me then that the Mergui Zelphusa was not represented 
ja the Museum*. 
The upper surface of the cephalothorax is minutely punctate. 
The ‘sont is somewhat granular between the orbits. Besides the 
vediea frontal furrow, which divides as usual the postfrontal 
‘ge, and the arcuate median portion of the cervical suture, which 
eporates the gastric from the cardiac region, no other inter- 
regional grooves are found on the upper surface; nevertheless 
on each side of the gastric region the upper surface is somewhat 
impressed in an oblique direction, from the epibranchial tooth 
towards the mesogastric region ; by these impressions the gastric 
region is separated from the epibranchial portions of the upper 
surface. The branchial regions are hardly at all inflated. The 
postfrontal ridge is distinctly indicated and interrupted, not 
only by the median frontal furrow, but also at each side of the © 
latter, in the middle, and near the lateral margins. The two 
median or internal portions, which are somewhat transversely 
rugose anteriorly, and which are separated from one another by 
the median frontal furrow, are a little more advanced than the 
lateral portions, from which they are completely separated. 
These lateral ridges are scarcely broader than the median, and 
are nearly straight and directed towards the epibranchial teeth, 
whereas the median portions are slightly arcuate. The lateral 
portions, however, are not continued as far as the epibranchial 
teeth, but are interrupted at some distance from them. Imme- 
diately behind that interruption, on each side of the upper surface, 
a short oblique rugose line is observed. The orbital margins are 
smooth and entire; the flattened external angles of the orbits are 
nearly right angles, and are therefore scarcely acute. The ex- 
ternal margin of the cephalothorax, between the external angle 
of the orbits and the epibranchial tooth, is smooth and entire. 
The epibranchial tooth is acute and prominent; and the lateral 
margins of the cephalothorax behind it are marked with many 
oblique piliferous lines. I may further add that the gastric region 
appears sometimes minutely rugose, immediately behind the post- 
* Gerstacker and Hilgendorf suppose that Telphusa hydrodromus, Herbst, is 
identical with 7. grapsoides, White. ‘To me, however, the latter appears to be 
distinct from the former species. In Z. grapsoides the distance between the 
epibranchial teeth is almost exactly the length of the cephalothorax, whereas 
in T. hydrodromus the breadth is in proportion to the length as 16:13. 
LINN. JOURN.—ZOOLOGY, VOL. XXII. a 
