CRUSTACEA OF THE MERGUI ARCHIPELAGO. 155 
The chelipedes of the male are, in most species, more or less 
elongate, the palm being nearly always longer than broad. Arms of 
the anterior legs of the male with “musical crest.” Ambulatory 
legs similar to those of Helice, those of the penultimate and 
antepenultimate pair being equal in length, and much longer 
than the legs of the second and fifth pair. 
Though this genus is closely allied to Helice I am, however, 
inclined to retain it, including in the genus of de Haan (the type 
of which is Helice tridens) those species which have the cephalo- 
thorax rather thick and more or less convex above, and the 
chelipedes short, with the palm higher than long. The genus 
Metaplax, on the other hand, may contain those species with a 
thinner and more depressed cephalothorax, which have the anterior 
legs more or less elongate, and the palms of the hands longer 
than high. 
The genus Paragrapsus, M.-Edw., of which I have been enabled 
to examine two species through the kindness of Prof. A. Milne- 
Edwards, is also closely allied to Metaplax, but differs by the 
front being much more prominent than the epistome. 
The genus Metaplax, as now defined, includes seven species, 
all of which inhabit the Oriental seas; five are described in this 
Report, the other two being Wetap. indicus, M.-Edw., and Metap. 
longipes, Stimps., from Hongkong. 
The five species of this collection may be distinguished thus :— 
( spinulose along the upper or anterior margins......... crenulatus. 
( Lobules of the 
orbital portion 
| very large, 6 in 
| number in the 
not —_spinulose adult male, and 
| along the upper rapidly decreas- 
Carpopodites or anterior mar- 25-30. 1 ING IN Size 44.2. dentipes. 
and propodites , gins. Number Lobules of the 
of the ambula- | of lobules or 4 orbital portion 
tory legs teeth of the in- small, 10-12 in 
fraorbital ridge number, and 
in the male slowly decreas- 
amounting to | \ ing) inisize! ee... distinctus. 
40-60. longer than 
| | Palm of the } broad ............ elegans. 
| hands of the | as long as 
N | male broad’? cssoestaas. intermedius. 
