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Show 5 4 0 DR. J. G. DE MAN ON CRUSTACEANS [Dec. 12, barbatus A. M.-Edw. *, a marine crab from New Caledonia, which has also been observed on the shores of Atjeli, Penang, and of the islands between Japan and Formosa, is the most closely related form. As regards the proportion between the length of the carapace and the greatest width of it in adult specimens, both species fully agree with one another, but in young individuals the carapace of barbatus is slightly broader in proportion to its length than that of 2)usi^us (de Man, I. c. p. 104). At nil ages, however, both in the male and in the female, the cephalothorax of barbatus is anteriorly distinctly broader in proportion to its length, as is proved by comparing the measurements of the length of the carapace and of the distance between the extraorbital angles ; the extraorbital teeth run therefore more obliquely with regard to the median line of the carapace in Ptych. pusillus than in Ptych. barbatus (figs. 1 and 6). In proportion to the greatest width of the carapace the front appeal's a little broader in barbatus ; it has the same form in both species, but the granulated line that runs immediately behind the frontal margin is, in the middle line of the carapace, contiguous to that margin in barbatus, whereas in Heller's species (fig. 2) both lines are distant from one another in the middle. In Ptych. barbatus the epigastric lobes are situated farther from the frontal border than in pusillus (figs. 1 and 6). In Ptych. barbatus the 2nd and the 3rd anterolateral teeth of the carapace are more salient and the incisions are deeper than in pusillus ; near the antero-lateral teeth the carapace of pusillus is somewhat granulated, but in barbatus not. The exognath of the external maxillipedes of the adult male of Ptych. barbatus is one-third broader than the ischium, and in the adult female it is just as broad or even very slightly broader than the ischium; in the adult male of pusillus the exognath appears a little less broad in proportion to the ischium, and in the female the ischium is decidedly broader than the exognath. The slight differences exhibited by the legs are of little importance. But for a few hairs on the outer side of the tip of the fixed finger in the female, the extremities of the fingers of barbatus are glabrous. Ptych. barbatus is smaller than pusillus and the habitat is different, the former being probably a marine species, the latter a freshwater one. An adult female of Pseudograpsus barbatus Rumph from the River Wukur, on the island of Flores, is lying before me (vide de Man, in Max Weber's ‘ Decapoden des Indisclien Archipels,' 1892, p. 317); it will be useful to indicate the differences between this specimen and the female of Ptych. pusillus Heller, since they much resemble each other. Both species, of course, differ at first sight by their external maxillipedes; the rounded antero-external angle of the merus-joint is less strongly produced in Pseudograpsus barbatus than in Heller's species, and the exognath * Ptych. barbatus is also described in Prof. Alcock's work : " Materials for a Carcinological Fauna of India-No. 6. The Bracbyura Catometopa or Grapsoidea," Journ. Asiatic Soc. Bengal, lxix. (2) no. 3, 1900, p. 406. |
