1880.] FROM CENTRAL AFRICA. 349 



olive, the front of the body-whorls being more or less stained by a 

 reddish earthy deposit. The spines and the keel are also of a 

 browner tint than the rest of the shell. Length 45 millims., greatest 

 diameter 31 ; aperture 35 long, 16 broad. 



This is perhaps tlie most remarkable species of freshwater Mollusca 

 yet discovered. Its strange form, the array of spines at the angles 

 of the volutions, the prolonged beak, the pretty sculpture, and the 

 lack of an epidermis give this shell a unique character among all 

 others. The number and proximity of the spines vary in different 

 specimens ; the largest shell has the unusual number of fourteen on 

 the last wliorl, five of them being quite close together near the 

 aperture. One example differs from the rest in having a narrow 

 olivaceous line around the middle of the body-whorl. 



Neothauma', nov. gen. 



Shell like that of the genus Vivipara, but having the aperture 

 effuse and sligiitly channelled at the base, and the outer lip rather 

 deeply yefc widely sinuated in the middle. Animal and operculum 

 luiknowu. 



The aperture in the genus Vivipara is, as a rule, more or less cir- 

 cular or ovate, and the continuous peritreme is generally almost 

 level or on one plane. In the present genus on the contrary, the 

 form of it is irregular and angular, and the labrum is deeply emar- 

 ginate, causing the level of the peristome to vary considerably. 



10. Neothauma TANGANYicENSE. (Plate XXXI. figs. 7-7c.) 

 Shell ovate, acuminate, solid, scarcely rimate, white, clothed with 



an olive-brown epidermis. Young shells exhibited two brown 

 bands upon the upper whorls and three on the last. Whorls 7, 

 roundly shouldered above, obliquely convexish at the sides, separated 

 by a very deep horizontal suture, sculptured with oblique flexuous 

 lines of growth and a few faintly impressed spiral striae. Last whorl 

 (with one exception) angular and keeled at the middle. Aperture 

 irregularly triangularly ovate, bluish white within, effuse at the 

 base. Columella thick, slightly arcuate, white ; callus reflexed, 

 almost concealing the umbilical perforation, joining the upper ex- 

 tremity of the outer lip ; the latter is thin, a little angular in the 

 middle at the termination of the keel around the whorl, and when 

 viewed laterally is seen to be deeply and widely sinuated. Length 

 53 millims., diam. 29 ; aperture 24 long, 19 broad. Another speci- 

 men, length 46 millims., diam. 29 ; aperture 23 long, 19 broad. 



The largest specimen whose dimensions are given above is of ab- 

 normal growth, and exhibits scarcely any trace of the strong angle 

 and keel which is so characteristic of the species. The colour bands 

 are distinct in the young shell, but with age entirely disappear. 



11. Planorbis sudanicus, Martens, Mai. Bliit. 1870, p. 35, 

 1874, p. 41 ; Novitates Conchyl. vol. iv. f\. 114. f. 6-9, 



This species is very like the West-Indian P. guadelupensis, but 

 ^ Froni jeos, new, and Qavfia, a wonder. 



