158 LITTORINID^l. 



Very probably belongs to the Litiopince, near Alaba, Diala, 



1. Plesiotrochus, n. sp. 



An interesting form of this very distinct new Genus Avhich 

 I have for several years intended to descrioe. The whorls are 

 characteristically concave. 



10 Mauritius ; coll. G. Nevill, Esq. 



1 Andamaus; coll. Dr. F. Stoliczka. 



2. Plesiotrochus [?] n. sp. 



2 Persian Gulf ; coll. W. T. Blanford, Esq. 



Sub-family FOSSABIN^, Stoliczka. 

 Genus RISELLA, Gray. 



Syn. Brit. Jtlus. 1840, type Trochus melanostoma, Gm. ; = Be>nbictum, 

 Philippi, Zeits. Malac. Ill, 1845. 



1. Rlsella plana. 



Trochus plana, Quoy, Voy. Astrol. 1832, " Port Western," Bass's Strait. ; 

 =Littorina australis, Gray, Beechey's Voy. 1839; var.=R. grisea, 

 Phil., Zeits. Mai. 1851, Hab. ? 



7 Australia; ex c. Asiat. Soe., Bengal [coll. Strange]. 

 4 South Australia ; ex c. British Museum and Miss Pelly. 



Agree with figure, in Conch. Cab. II, of R. grisea, Phil. 



var. 



1 Port Mackay ; ex Mus. Godeffroy [as " var. B., Crosse "]. 

 30 Port Jackson ; coll. Dr. J. C. Cox and G. Nevill, Esq. 



2. Risella imbricata. 



Littorina imbricata, Gray, Beechey's Voy., 1839 [sine Hab.] ; = Risella 

 Jcielmannseggi, Frauenfeld, 1866, N. Zealand. 



1 Australia; ex c. G. Nevill, Esq. 



