CRUSTACEA OF THE MERGUI ARCHIPELAGO. 137 
DIoxIPPE*, nov. gen. 
Cleistostoma, de Haan, partim. 
The genus Cleistostoma was founded by de Haan upon two 
Japanese species—C. dilatata and C. pusilla. An examination 
of a large number of specimens of the latter species which I 
found in a small collection of Japanese Crustacea, kindly pre- 
sented to me by Dr. Anderson, now makes it very probable that 
the two species of Clezstostoma described in the ‘ Fauna Japo- 
nica’ are not so closely allied to one another as de Haan sup- 
posed, and that they are even generically distinct. De Haan 
had only young male specimens of C. pusilla at his disposal, 
whereas my specimens are of a larger size, and there are both 
males and females among them; so that I have been enabled 
to observe some characters that were overlooked by de Haan. 
I find that the merus-joint of the external maxillipeds of C. 
pusilla has not the same quadrate form of the ischium-joint, but 
that the outer foot-jaws of this species resemble much more 
those of some Dotille. The external maxillipeds of Cleistostoma 
dilatata, figured by de Haan, on the contrary, have a different 
form, their merus-joint being as quadrate as the ischium-joint. 
Moreover, the meropodites of the ambulatory legs of C. pusilla 
present traces of the remarkable “tympana” which are so cha- 
racteristic of the true Dotille and Scopimere; though small, they 
are quite distinct on the outer surface of the meropodites of the 
last pair of legs in the male. These “tympana’”’ were over- 
looked by de Haan, who had only small specimens at his dis- 
posal, as I have already observed. Furthermore, the whole outer 
appearance of Cleistostoma dilatata is quite different from that of 
C. pusilla, the lateral margins of the cephalothorax of the former 
Species presenting none of the small emargination immediately 
behind the external orbital angles which characterizes C. pusilla, 
and is also observed in many species of Dotilla, and the front 
is much broader in C. dilatata than in the other species. 
The Mergui collection contains an interesting new species, 
which agrees in many essential characters with Cleistostoma 
pusilla, though specifically distinct. 1 propose, therefore, for 
these two species the new genus Déioxippe, which may be dis- 
tinguished from the genera Dotilla and Scopimera chiefly by 
* Dioxippe, one of the Heliads, 
