1880.] FROM CENTRAL AFRICA. 345 



generic forms and unlike any other, either recent or fossil. The former 

 with its spine-bearing whorls calls to mind certain marine rather than 

 lacustrine genera ; and the latter, although very vivipariform, yet 

 differs from all the species of that family in possessing a sinuated 

 outer lip and an effuse base to the aperture. Of the terrestrial shells 

 one, Limicolaria nilotica, has previously been recorded from more 

 northern Nilotic regions ; and the same observation applies to five 

 species from the lake, viz. AmpuUaria ovata, Planorhis sudanicus, 

 Miitela exotica, Unio niloticus, and j^tkei-ia elliptica. 



1. AcHATiNA (Limicolaria) nilotica, Pfeiifer. 



Bui hnus niloticus, Pfr. P. Z, S. 18G1, p. 24 ; Mai. BUit. 18G1, 

 p. 14; Mon. Ilel. vi. p. 86; Mon. Hel. viii. p. 2C8 {Limico- 

 laria nilotica). 



Achatina {Limicolaria') nilotica, Pfr. ; Martens, Mai. Bliit. 186.5, 

 p. 196, 1870, p. 32 (as Achatina nilotica); Novitates Conch, iv. 

 pi. 110. f. 1-3. 



Tliis sjjecies appears to be common in the Upper-Nile region. It 

 was first collected in the White-Nile district, and subsequently by 

 Dr. Schweinfurth near the Gazelle River. 



A narrowly ovate specimen is 1 1 1 millims. in length and only 50 

 in diameter, and the aperture occupies only a little more than half 

 the length, whilst in a specimen from the White-Nile district it 

 equals y^^- of the total length. 



2. Achatina (Limicolaria) martensiana, sp. nov. (Plate 

 XXXI. figs. 1, la). 



Shell rimate, rather solid, oblong, turreted, reddish towards the 

 apex, elsewhere dark purple-red or almost black, variegated with 

 oblique, more or less zigzag, opaque creamed-coloured stripes, some of 

 which extend from suture to suture, others only a short distance from 

 the top of the wliorls. The latter are 71 in number, scarcely convex 

 or almost flat, and ver}^ feebly constricted beneath the suture. The 

 upper ones are finely granosely decussated, the last and the penul- 

 timate being smooth and merely marked with the oblique incremen- 

 tal strise. All exhibit a fine plication or puckering beneath the 

 suture, beneath which an impressed line is sometimes observable 

 upon the last and pi'cceding volutions. Aperture bluish wiihin, 

 displaying more or less of the external strii)ing, vertical, equalling 

 about two fifths of the shell's length. Columella suberect, bluish 

 and dark violet, scarcely forming any angulation at the base with the 

 lower margin of the peritreme. Length 36 milhms., diam. 17; 

 aperture 14| long, 8 wide. 



This handsome shell approximates very closely to A. heuglini of 

 Martens in form, but has certain diiferences in colour and sculpture, 

 which, however, ma}' prove to be only varietal. A. heuglini, from 

 South Abyssinia and the Gazelle Kiver, is said to be regularly striated, 

 and of a horny lutescent colour flamed with red. A. martensiana, 

 on the contrary, is finely granosely decussated upon the spire, and the 

 coloration is very rich and striking. The dark purplish red, which 



