1906.] OF THE THIRD TANGANYIKA EXPEDITION. 535 



(text-fig. 9 B), and the absence of a large chitinoiis 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 ISTyasa 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 [jSiuMmann) ; Dromira Bay, Lake Nyasa, 

 June 19, 1904, among algse &c. {Cunnington), 



Arrhenurus plenipalpis Koen. 



A male Arrhemijnts found in the same locality as the preceding 

 species seems to be referable to A. plenipalpis Koen. On com- 

 parison, however, with the description and figures of this species 

 some rather puzzling difierences 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 ISTyasa specimen is unnecessary. Althovigh Dr. Koenike 

 describes the present species in the letterpress of his paper (3) 

 under the name of A. jdeiiipalpis, 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-B^ ; German East Africa (Quili- 

 mane) ; Dromira Bay, Lalce Nyasa (Cunnington). 



Bibliography. 



1. Koenike, F. — " Die von Herrn Dr. F. Stuhlmann in Ostafrica 



gesammelten Hydrachniden." Jahrb. Hamburg, wissenschaft. 

 Anstalten, 1893, x. 



2. PiERSiG, R. — " Bemerkungen zur Hydrachnidenkunde." Zool. 



Anz. 1897, XX. pp. 59-61. 



3. Koenike, F. — " Hydrachniden : Fauna von Madagascar und 



Nossi-Be." Abhand. Senckenb. Ges. 1898, xxi. pp. 297-435. 



4. PiERSiG, R. — " Hydrachnida} und Halacaridse." Das Tierreich, 



1901. 13. Lieferung. 



