349 



linea cardinal! antice compressa tuber culala t post ice latiore, 

 paucis rugis arata. 



2. Unio burtoni, n. sp. (PL XLVII. fig. 1.) 



Shell small, oval, rather thin, somewhat pointed behind ; umbones 

 small, not eroded ; pale olive, concentrically furrowed, and sculptured 

 more or less with fine divaricating lines ; anterior teeth narrow, not 

 prominent ; posterior teeth laminar ; pedal scar confluent with ante- 

 rior adductor. 



Length 12, breadth thickness 5^ lines. 



Testa parva, ovalis, tenuiuscula, postice subattenuata ; umbonibus 

 parvis, acuminatis ; epidermide pallide olivacea ; valvis lineolis 

 divaricatis, decussatim exaratis ; dentibus cardinalibus angustis, 

 hand prominentibus. 



3. Lithoglyphus zonatus, n. sp. (PI. XLVII. fig. 3.) 

 Shell orbicular, hemispherical ; spire very small ; aperture large, 



very oblique ; umbilicus wide and shallow, with an open fissure in 

 the young shell ; lip continuous in front with the umbilical ridge ; 

 columella callous, ultimately covering the fissure ; body- whirl flat- 

 tened, pale olivaceous, with two brown bands, darker at the apex ; 

 lines of growth crossed by numerous oblique, interrupted striae. 

 Diameter 5-6, height 3 lines. 



Testa orbicularis t hemisphcericajat e umbilicata(apud juniores rimata\ 

 spira minuta ; apertura magna, valde obliqua ; labio calloso {in 

 testa adulta rimam tegente): pallide olivacea, fasciis duabus fuscis 

 zonata ; lineis incrementi striolis interruptis oblique decussatis. 



4. Melania (Melanella) nassa, n. sp. (PI. XLVII. fig. 4.) 

 Shell ovate, strong, pale brown, with (sometimes) two dark 



bands ; spire shorter than the aperture ; whirls flattened, orna- 

 mented with six brown spiral ridges crossed by a variable number 

 of white, tuberculatecl, transverse ribs ; base of body-whirl with eight 

 tuberculated spiral ridges variegated with white and brown ; aper- 

 ture sinuated in front ; outer lip simple ; inner lip callous. 

 Length breadth b\ lines. 



Testa ovata, solida, pallide fusca, zonis 2 niqricantibus aliquando 

 notata ; spira apertura breviore ; anfractibus planulatis, lineis 6 

 fuscis spiralibus et costis tuber culati^ornatis ; apertura antice 

 sinuata ; labro simplici ; labio calloso^B^ 



P.S. July 2 7th. — In addition to the foregoing^shells, several others 

 were collected by Capt. Speke, when employed, under the command 

 of Capt. Burton, in exploring Central Africa in the years 1856-9 ; 

 these were deposited in the first instance with the Geographical 

 Society, and are now transferred to the British Museum. 



A specimen of Ampullaria (Lanistes) sinistrorsa, Lea, and odd 

 valves of two species of Unio, both smooth and olive- coloured, were 

 picked up in the Ugogo district, an elevated plateau in lat. 6° to 

 7° S., long. 34° to 35° E. 



