42 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



DESCRIPTION OF 



LEPTOPOMA (TROCHOLEPTOPOMA) MITCHELLS, n.sp., 



FROM BORNEO. 



By Edgar A. Smith, F.Z.S., etc. 



Read 8th December, 1899. 

 Leptopoma (Trocholeptopoma) Mitchells. 



Testa anguste umbilicata, conica, tenuis, pellucido-albida, periostraco 

 tenuissirno opaco-albido, lineis pellucidis longitudinalibus irregularibus 

 interrupto, induta ; spira elate conica, ad apicem vix acuta ; aufractus 

 6 convexiusculi, liris spiralibus tenuissimis 6-7, striisque gracillimis 

 intercalatis ornati, lineis increnienti obliquis sculpti, ultinius ad 

 medium carinatus, carina antice fere evanida, infra leviter convexus, 

 concentrice striatus et subliratus, baud clescendens ; apertura magna, 

 subcircularis ; peristoma tenue, albidum, margine externo conspicue 

 expanso, columellari renexo, crassiore. Alt. 14-5 mm. ; diam. niaj. 

 14 - 5, min. 10*5 mm. 



Hal.— Sarawak, North Borneo. 



V 





Leptopoma Mitchellce, n.sp. 



In form tbis species ratber closely resembles L. Bourguignati, Issel, 1 

 but it differs in the character of the periostracum and sculpture, the 

 fine spiral lirae being more numerous and the interstices finely spirally 

 striated. It is remarkable for tbe excessively thin, opaque- white 

 periostracum, which is interrupted by translucent lines radiating from 

 the suture. The spiral threads are not very distinct, and only a little 

 stronger in some specimens than the intervening striae. The peri- 

 pheral keel in some examples is also more acute than in others. The 

 operculum is thin, corneous, and consists of eight whorls. Named 

 in honour of Lady Mitchell, widow of the late Governor of the Straits 

 Settlements, through whose instrumentality the specimens were 

 obtained. The type and a second example have been presented to 

 the British Museum (Natural History) by Mr. J. H. Ponsonby. 



1 Ann. Mus. Genova, vol. vi (1874), p. 428, pi. vi, figs. 7, 8. 



