CRUSTACEA OF THE MERGUI ARCHIPELAGO. 97 



iBformed me then that the Mergui Telphusa was not represented 

 in the Museum*. 



The upper surface of the cephalothorax is miuutely punctate. 

 The front is somewhat granular between the orbits. Besides the 

 median frontal furrow, which divides as usual the poatfrontal 

 ridge, and the arcuate median portion of the cervical suture, whicli 

 separates 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 th.e epibranohial 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 tlian 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 epibrancliial 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 mai'ked 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 T. grajpsoides. White. To me, however, the latter appears to be 

 distinct from the former species. In T. grapsoides the distance between the 

 epibranchial teeth is almost exactly the length of the cephalothctrax, whereas 

 in T. hydrodromus the breadth is in proportion to the length as 16 : 13. 



LINH. JOUBN. — ZOOLOGY, TOL. XXII, 1 



