The Non-Marine Mollusca of Portuguese East Africa. 191 



Isidora {Physopsis) africana (Krs.), 1848. 



1848. Physopsis africana Krs., Sudafr. Moll., p. 85, pi. 5, fig. 14. D.F. 



Hah. L. Marques. Tette (Peters ; Kirk ; Penther) ; Lebombo Marsh, 

 Rikatla (Junod) ; Wanetsi R., Magude District (Bell Marley). 



It is possible that some of the foregoing records refer in reality to the 

 succeeding species. 



Isidora {Physopsis) globosa (Morelet), 1866. 

 (Plate VIII, figs. 8-15.) 



1868. Physopsis globosa Morel., Voy. Welwitsch, p. 93, pi. 9, fig. 4. D.F. 



Hah. L. Marques. Lebombo Marsh, Rikatla (Junod) ; Delagoa Bay 

 (Cawston). 



The range of this very variable species extends laterally across the 

 continent from Angola, through Rhodesia and Nyasaland, to Delagoa Bay. 

 Some Delagoan examples correspond well with Morelet's type, while others 

 differ considerably inter se in length of spire and form of aperture, but 

 all appear to be conspecific. In addition to the slight difference in the 

 radula mentioned later, the shell is practically always to some extent 

 rimate, and can thus be separated without much difficulty from /. {Phy- 

 sopsis) africana (Krs.). 



External features of animal and pallial organs. — The foot is broad 

 and bluntly pointed at the hind end. The tentacles are slender and 

 rather long, with the eyes situated at their inner bases (PI. VIII, fig. 13). 

 At their outer bases there is a rounded, flattened lobe on each side, such as 

 was first described by Adanson in Bulinus senegalensis MiilL* The male 

 opening is situated beneath the posterior corner of the lobe on the left side ; 

 the female opening is under the mantle-edge. 



The orifice of the mantle-cavity is large (PI. VIII, fig. 8). At its inner or 

 right side, posterior to the anus, there is a large grey pallial lobe, which is 

 thrown into numerous vertical folds, the bigger folds being subdivided by 

 smaller ones. This is the characteristic folded gill of the genus Isidora, 

 which is found not only in the various African members of the genus, but 

 also in those occurring in Madagascar, Tasmania, New Zealand, etc., f as 

 well as in the related genus Miratesta from Celebes. { Anterior to the 

 anus there is a simple, less prominent, white lobe, which forms the lip of the 

 so-called pulmonar}' siphon. 



The head and foot are rather light grey, the hind end of the foot and the 

 top of the head being the darkest. The mantle-edge is pale, but the roof 



* Hist. Nat. du Senegal, Hist, des Coquillages, 1757, p. 6, pi. i, fig. Jg^. 



t Pelseneer: Arch, de Biol, vol. xiv, 1896, pp. .365, 372, pi. xv, figs. 10-11. 



% Sarasin : Die Siisswasser Mollusken von Celebes, 1898, p. 76, pi. xii, figs. 165-166. 



