CRUSTACEA OF THE MERGUI ARCHIPELAGO. 181 
appear in this species quite smooth and ungrooved. On each 
side of these smooth regions there are therefore three principal 
grooves nearly parallel to one another and directed obliquely 
forwards and inwards. ‘The lateral margins are ciliate, present 
a small emargination immediately behind the external angles of 
the orbits, and are directed obliquely backwards to the bases of 
the fourth pair of legs. 
In its general appearance the cephalothorax of D. brevitarsis 
resembles that of D. swlcata, but the upper surface is grooved in 
a different manner. The upper surface is a little broader than 
long, a little convex longitudinally as well as transversely, and 
distinctly suleate. The front resembles that of D. sulcata, is 
strongly deflexed, as in that species, but is less narrowed and 
more rounded anteriorly. It is broadly grooved, the groove 
occupying, as in D. sulcata, nearly the whole breadth of the front ; 
this grocve is prolonged backwards, in the middle line of the 
cephalothorax, to the posterior cardiac region, where it is a little 
narrowed, and issues into a transverse groove, which runs parallel 
to the posterior margin of the carapace at a short distance 
from it. The five-rayed star of grooves, which occurs in D. sud- 
cata anteriorly, is absent in D. brevitarsis. The lateral margin 
is ciliate, and presents a slight emargination immediately behind 
the external orbital angle, as in D. swleata; about its middle, 
however, the margin is a little curved inward, so that its course 
is rather sinuous, and it terminates above the base of the 
last pair of legs. The lateral margin is bordered, on the upper 
surface of the carapace, by a groove which corresponds to 
the groove (a) of D. sulcata, described above ; another groove, 
proceeding on the epibranchial region, issues into the lateral 
groove at about the middle of its length. On each side of 
the upper surface another transverse groove is found a little 
behind and parallel to the upper orbital margin, proceeding 
from the internal angles of the orbits towards the anterior 
portion of the lateral margin; this groove, into which a small 
and short groove issues about the middle of its posterior mar- 
gin, is separated from the upper margin of the orbits by an 
ovoid prominence. Furthermore, those portions of the upper 
surface which lie between the broad median furrow and the 
grooves (a) of the lateral margins are somewhat unequal. The 
elevated portions of the upper surface, by which the grooves are 
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