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Show 1901.] CRUSTACEAN FROM THE SOUDAN. ll'l Length of the legs of the last pair 53 Leugth of the meropodites of these legs 17 Breadth of the meropodites of these legs 5f Length of the dactylopodites 11 Thickness of the cephalothorax 21 Remarks on Potamon (Potamonautes) hilgendorh* Pfeffer. Prof. Pfeffer, of the Xaturhistorisches Museum of Hamburg, was so kind as to present m e with two type specimens of Telphusa hilgendorfi Pfeffer, both males from tjngiiu. As Pfeffer's description (' Uebersicht der von Herrn Dr. Fr. Stuhlmann in Aegypten, auf Sansibar und dem gegeniiberliegenden Festlande gesammelten Reptilien, Amphibien, Fische, Mollusken und Krebse,' Hamburg, 1889, p. 32) is very short, the following remarks will, I think, be welcome. The larger specimen has lost its chelipedes ; in the other both are present, but Dr. Pfeffer had added two detached chelipedes, that, as regards their size, should belong to the larger male. In the first place I will remark that, as Pfeffer likewise writes to me, the true Pot. hilgendorfi Pfeffer is a different species from that which has recently been described under the same name by Hilgendorf ('Die Land- uud Susswasser-Dekapoden Ostafrikas,' 1898, p. 9, fig. 3), and which inhabits the country around Kilimanjaro. The cephalothorax of both males is depressed, especially behind the cervical suture. The gastric region appears, however, very slightly arcuate, both transversely and from before backwards. Hilgendorf, on the contrary, describes the cephalothorax of his species as " deutlich gewolbt." In Hilgendorf's species the anterolateral margin of the carapace is described as extending laterally beyond the Outer orbital angle somewhat farther than the orbits are broad, but in the type specimens of Pot. hilgendorfi Pfeffer they extend laterally somewhat less than the orbits are broad. In the species described by Prof. Hilgendorf the lateral portions of the cervical suture are indistinct and invisible ; in Pfeffer's types, however, they are deep and distinctly developed, though not reaching to the postfrontal crest. In both species an epibranchial tooth is ivanting. That part of the lateral margin which is situated between the rather acute extraorbital angle and the lateral extremity of the postfrontal crest is very oblique, distinctly granulated, and makes a right angle with the upper margin of the orbits ; in Hilgendorf's species, on the contrary, the outer orbital angle is described as "stumpfwiuklig." In the young male the lower margin of the orbits presents no trace of a hiatus; but just below the extraorbital angle in the larger male I observe a quite shallow incision only on the left side; in the species from Kilimanjaro, however, the incision is small, but usually deep. The antero-lateral margin, the postfrontal crest, and the orbital mar"ins are distinctly granular or crenate, the postfrontal crest is rather prominent and only interrupted by the mesogastric suture |