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Show 1 9 0 6 .] OF THE THIRD TANGANYIKA EXPEDITION. 5 3 5 (text-fig. 9 B), and the absence of a large chitinous disc-bearing plate on each side of the genital field. The genital discs are imbedded in the soft skin of the body. The colouring of the Nyasa specimens is pale green with brownish blotches on the dorsal surface, the central csecal area is yellow, and the legs and palps green. Localities. Zanzibar (Stuhlmann); Dromira Bay, Lake Nyasa, June 19, 1904, among algae &c. (Cunnington). A r r h e n u r u s p l e n ip a l p is Koen. A male Arrhenurus found in the same locality as the preceding species seems to be referable to A. plenipalpis Koen. On comparison, however, with the description and figures of this species some rather puzzling differences are apparent, notably the presence in the Nyasa specimen of a chitinous petiolus-like organ. This structure is situated in the middle line of the body and projects in the posterior indentation of the body appendage in the form of a short bluntly-pointed process (text-fig. 94 A). This, however, is a sexual characteristic, which in the Micrurus section of the genus may possibly be prominent only in some specimens or under certain conditions. The forked chitinous organ in the centre of the appendage, which Dr. Koenike calls the " Hautgebilde," seems to differ somewhat in outline, but I suspect that this may be due to the preservation of the specimens or to slight differences in the drawing. Otherwise the Nyasa mite agrees closely with the description of A. plenipalpis (3), and a full description of the Nyasa specimen is unnecessary. Although Dr. Koenike describes the present species in the letterpress of his paper (3) under the name of A. plenipalpis, and makes reference to plate xxi. figures 36-40, yet in the explanation of the plates these particular figures are referred to as representing a new species, pertusus (page 427). No explanation is given for this change of name. The species is included in Dr. Piersig's recent work on the Hydrachnida (4) as A . plenipalpis. Localities. Madagascar ; Nossi-B6 ; German East Africa (Quili-mane); Dromira Bay, Lake Nyasa (Cunnington). Bibliography. 1 . K o e n ik e , F.- " Die von Herrn Dr. F. Stuhlmann in Ostafrica gesammelten Hydrachniden." Jahrb. Hamburg, wissenschaft. Anstalten, 1893, x. 2. P ie r s ig , R.-" Bemerkungen zur Hydrachnidenkunde." Zool. Anz. 1897, xx. pp. 59-61. 3. K o e n ik e , F.-" Hydrachniden : Fauna von Madagascar und Nossi-Be." Abhand. Senckenb. Ges. 1898, xxi. pp. 297-435. 4. P ie r s ig , R.-" Hydrachnidse und Halacaridse." Das Tierreich, 1901. 13. Lieferung. |
