1893.] SHELLS EBOiL BBITISH OKUtBAL AEBICA. 633 



tution has been indebted on pre\aous occasions for valuable collec- 

 tions from the Cameroons and the neighbourhood of Mount Kilimar 

 njaro. 



The most interesting specimens of the present collection are 

 those obtained at Lake Mweru, a locality from which no Mollusca 

 have as yet been recorded. This lake lies to the south-west of 

 Lake Tanganyika, with which, however, it has no connection, as 

 would be presumed by the difference of the Molluscan faunas so 

 far as they are at pi-esent known. All the species from Lake 

 Mweru are undescribed with one exception, and this appears to be 

 a dead woi'u example of Lanistes ovum. The other species in- 

 clude two forms of Viviparus, two Cleopatrce, three Melaiiice, a 

 very remarkable winged Unio, and examples of two or three other 

 species of that genus, but represented by specimens too young or 

 too worn to be determined. 



Forms of aU these genera occur in Tanganyika, and one of the 

 species belongs to that group of Vinparus wliich, chai'acterized 

 by the aperture being somewhat ett'use anteriorly and the outer 

 Up sinuated, was described by tlie writer in these ' Proceedings ' 

 for 18S0 as a new genus from Tanganyika, under the name of 

 Neothamna. 



1. ENifBA JOHXSTOJfi. (Plate LIX. fig. 1.) 



Testa elongata, ci/limlracea, crassiuscula, rimata, Jlavo-viridis, 



parum nitida ; atifractus 6, coave.viuscidi, ohliqiie fortiter striati, 



superiores quatuor regulanter crescenies, ultimus et penultinms 



longe majores, ultimus elongatus, sup^-a ajperturam Icevior et suh- 



complanatus, pi-imo jterohlique descendens, sed ad lahrum hreviter 



ascendeiis; spira obtusissima ; sutura mediocriter profunda; 



apertura sahovata, intits sordide albida, longit. totius i paulo 



supierans, denticulo unico parietali munita ; peristoma album, 



incrassatum, anguste rejlexum, margirdbus callo crassiuscula 



junctis. 



Longit. 20 millim., diam. 10 ; apertura 8 longa, 5-| lata. 



Hab. Port Johnston, Upper Shire Eiver {A. W7ii(te). 



This interesting shell is qiute unlike any other known species, 



but recalls the form of some of the Mauritian Gonospirce, e. g. 



G. modiolus, Perussac, although the relative proportion of the whorls 



is quite different. The oblique stride are distinct and thread-like, 



but less observable upon the body-whorl above the aperture, where 



the surface has a faintly flattened appearance. With this species 



I have associated the name of H. H. Johnston, Esq., the spirited 



Commissioner of this Country in British Central Africa, and the 



donor to the Museum of the specimens. 



2. EirauA KAEONGANA. (Plate LIX. fig. 2.) 



Testa cylindracea, rimata, alba, nitida ; anfracttis 7, lente accres' 

 ccntes, Iceves, leviter convexiusculi, sutura profunda vix obliqiia 

 sejuncii ; spira cglindrica, ad apicem obtuse conica ; anfr. ul- 

 timu^s antice liaud descendens vel ascendent, pone labrum profunde 



43* 



