284 Zoological Society. 



The large size of this species, and its convex form, distinguish it 

 from O. otis, and its absence of bands, and the outer lip not being ex- 

 panded, from O. sonata, Gould, the only two species at present known 

 to me. 



5. Note on Nematura, by A. Adams. 



The genus Nematura, established by Mr. Benson, appears to have 

 the closest affinity with Bithynia of Leach, but the horny opercu- 

 lum, with grooved margins, and the contraction of the aperture, will 

 distinguish them. There appear to have been found at present but 

 six species, three of them known, and three here indicated for the 

 first time ; in the rivers and streams of the East are doubtless many 

 more ; they are usually found adhering to the imder surface of dead 

 floating leaves. 



1. Nematura Delt^, Benson. N. testd magnd, pallidh fulvd, 

 globosd, Icevi ; aperturd orbiculari, peritremate simplici. 



Mus. Cuming. 



2. Nematura minima, Benson. N. testd parvd, corned, semi- 

 pellucidd, ovali, spird subproductd ; politd, fasciis rufis sub- 

 obsoletis ornatd; aperturd orbiculari, peritremate simplici. 



Mus. Cuming. 



3. Nematura polita, Sowerby. N. testd magnd, castaneo- 

 fuscd, compressd, subvaricosd; aperturd ovali, peritremate an- 



tice striata ; regione umbilicali lird callosd circumdato ; punc- 

 tato-striatd. 

 Mus. Cuming. 



4. Nematura olivacea, A. Adams. N. testd ovatd, opacd, 

 olivaced, viridi-fusco reticulatd ; aperturd ovali, spird elevatd, 

 apice decollato, peritremate simplici. 



Mus. Cuming. 



5. Nematura glabrata, A. Adams. N. testd magnd, ovatd, 

 non compressd aut varicosd, subviridi-corned ; spird acuta, 

 apice acuminata, Icevi, politd; aperturd orbicidari, angustatd, 

 peritremate nigra. 



Hah. Penang. Mus. Cuming. 



6. Nematura puncticulata, A. Adams. N. testd medioeri, 

 pallide fulvd, compressd, anfractu ultimo gibbosa, et subangu- 

 lato ad latera, lineolis punctatis transversis ornatd, peritre- 

 mate simplici. 



Hub. Eastern Islands. Mus. Cuming. 



6. A Monograph of the recent species of Rimula, a genus 



OF Mollusca, belonging to the family Fissurellid^. 



By Arthur Adams, R.N., F.L.S. etc. 



The genus Ritnula of Defrance has been usually confounded with 

 Puncturella of Lowe, or the Cemoria of Leach, but it is at once 



