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Show 1 9 0 5 .] ON CRUSTACEANS PROM CHRISTMAS ISLAND. 5 3 7 to. On Species of Crustacea of the Grenera Ptychognathus Stimps. and Palcemon Fabr. from Christmas Island. By Dr. J. Gr. de M a n , of Ierseke, Holland. [Received October 20, 1905.] (Plates XYII. & XVIII.*) The Crabs and Prawns described in this paper were sent me for examination by Dr. W. T. Caiman, of the British Museum. They were collected by Dr. R. Hanitsch, of the Raffles 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 [i. e. when Dr. Andrews was on the island in 1 8 9 7 - 1 8 9 8 ] . " 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 carefully 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. P t y ch o g n a th u s pu s il lu s Heller. (Plate XYII. figs. 1 -5 .) Ptychognathus pusillus Heller, Crustaceen der Novara Reise, 1865, p. 60. Ptychognathus pusillus de Man, in Zoolog. Jahrb. (Spengel), vol. ix. 1 8 9 5 , Abth. f. Syst. p. 9 9 , Taf. 2 8 . fig. 2 2 . 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 1 8 9 5 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 individual of another known species, perhaps Ptych. pilipes A. M.-Edw., from Celebes, or Ptych. intermeclius de M., from the Moluccas (I. c. p. 1 0 0 ). 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 tliere-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. 3 6 * |
