The Non-Marine Mollusca of Portuguese East Africa. 141 



Genus Trachycystis Pilsbry, 1893. 

 Trachycystis aenea (Krauss), 1848. 



1848. Helix aenea Krs., Sudafr. Moll., p. 75, pi. 4, fig. 18. D.F. 



1892. „ {Pella) burnupi M. and P., A.M.N.H. x, p. 239, pi. 13, 

 fig. 6. D.F. 



Hab. L. Marques. Cape Delagoa (Plant) ; Delagoa Bay (Connolly). 



The widely distributed Natalian species so well known as T. burnupi 

 (M. and P.) can unfortunately no longer retain that name, typical examples 

 from Pietermaritzburg having been compared with the type of T. aenea 

 (Krs.), and found to be absolutely identical. 



It is interesting to note that all the shells collected at Delagoa Bay, 

 both by Plant and the present writer, have a slightly, but noticeably, more 

 narrow umbilicus than is usually found in specimens from Natal, which 

 suggests that they may have bred true to this small peculiarity for over 

 fifty years. 



Trachycystis ambigua Conn., 1922. 

 (Plate IV, fig. 9.) 



1922. Trachycystis ambigua Conn., A.M.N.H. x, p. 116. D. 



Hab. L. Marques. Headwaters of R. Inyamkarrara, 25 miles N.W. of 

 Macequece (type, Cressy) ; Lebombo Marsh, Rikatla (Junod). 



Nyasaland. Mt. Chiradzulu (Johnston). 



S. Rhodesia. Vumbu Range, near Umtali, 7000 ft. (Arnold). 



The largest specimen seen is 4-85 mm. in maximum diameter. 



A member of the puzzling group which includes inclara Morel., coxi 

 Preston, and shilwaneensis Conn., from the last of which, its nearest ally, it 

 differs in having a very slightly lower spire and narrower whorls, in the 

 spiral striae being a little weaker above and further apart on the base, and 

 in being almost imperforate, whereas in shilivaneensis there is a very minute, 

 but clear, umbilicus. 



Trachycystis sericea Conn., 1922. 

 (Plate IV, fig. 10.) 



1922. Trachycystis sericea Conn., A.M.N.H. x, p. 116. D. 



Hab. L. Marques. District 16 miles N. of Macequece, 4500 ft. (Cressy). 



S. Rhodesia. Six miles from Penhalonga, 6000 ft. (Miss Grey). 



Perhaps nearest to T. aulacophora (Ancey) from which it chiefly differs 

 in its deeper suture and more silky appearance ; its perforation is much 

 narrower than that of T. riviilaris (Krs.) or T. ordinaria M. and P. 



