1905. ] ON CRUSTACEANS FROM CHRISTMAS ISLAND. 537 
6. On Species of Crustacea of the Genera Ptychognathus 
Stimps. and Palemon Fabr. from Christmas Island. 
By Dr. J. G. pr May, of Terseke, Holland. 
[Received October 20, 1905.] 
(Plates X VIT. & XVITI.*) 
The Crabs and Prawns described in this paper were sent me 
for examination by Dr. W. T. Calman, of the British Museum. 
They were collected by Dr. R. Hanitsch, of the Raftles Museum, 
Singapore, who wrote to Dr. C. W. Andrews regarding them : 
“The Prawn and the Crab were obtained from a small, artificial 
freshwater pool, on Christmas Island, above the waterfall, which 
probably did not exist in your time [7. ¢. when Dr. Andrews was 
on the island in 1897-1898].” Dr. Andrews adds that at the 
' time of his stay on the island the stream in question was a very 
small thread of water, trickling down the precipitous hill through 
thick bush, without pools of any size or depth, and that he care- 
fully explored it for Crustacea without finding any. Of course 
it is just possible that they may have existed in some pools not 
visited by him. 
PrycHo@NnaTHus PusiLLus Heller. (Plate XVII. figs. 1-5.) 
Ptychognathus pusillus Heller, Crustaceen der Novara Reise, 
1865, p. 60. 
Ptychognathus pusillus de Man, in Zoolog. Jahrb. (Spengel), 
vol. ix. 1895, Abth. f. Syst. p. 99, Taf. 28. fig. 22. 
One male and one female without eggs from a freshwater pool 
on Christmas Island. 
Ptychognathus pusillus Heller was founded, forty years ago, on 
a single female specimen collected by the ‘Novara’ Expedition on 
the Nicobar Islands; Heller did not figure his species. A new, 
detailed description, illustrated by several figures, of this type- 
specimen, preserved in the Museum of Vienna, appeared in 1895 
in my paper on the Decapod Crustacea gathered by Captain Storm 
in the Indian Archipelago: I suggested in this description that 
Ptychognathus pusillus should be regarded either as a distinct 
species, the male of which was still unknown, or as a young indi- 
vidual of another known species, perhaps Ptych. pilipes A. M.-Edw., 
from Celebes, or Piych. intermedius de M., from the Moluccas 
(l.c.p. 100). Ptychognathus pusillus, however, apparently a rare 
freshwater crab, has not been met with during the long period 
of forty years, and its rediscovery on Christmas Island is there- 
fore particularly interesting, especially because not only the female 
was found, but also the male, which hitherto was unknown. 
The two specimens prove that Ptych. pusillus Heller is a “ good 
species,” different from all its congeners. 
* For explanation of the Plates, see p. 550. 
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