158 LITTORINIDE. 
Very probably belongs to the Litiopine, near Alaba, Diula, 
&e. 
1. Plesiotrochus, n. sp. 
An interesting form of this very distinct new Genus which 
I have for several years intended to descrive. The whorls are 
characteristically concave. 
10 Mauritius; coll. G. Nevill, Esq. 
1 Andamans; coll. Dr. F. Stoliczka, 
2. Plesiotrochus [?] n. sp. 
2 Persian Gulf; coll. W. T. Blanford, Esq. 
Sub-family FOSSARINZ, Stoliczka. 
Genus RISELLA, Gray. 
Syn. Brit. Mus. 1840, type Trochus melanostoma, @m. ; = Bembicium, 
Philippi, Zetts. Malac. ITT, 1845. 
1. Risella plana. 
Trochus plana, Quoy, Voy. Astrol. 1832, “ Port Western,’ Bass’s Strait ; 
=Littorina australis, Gray, Beechey’s Voy. 1839; var.=R. grisea, 
Phil., Zeits. Mal. 1851, Hab. ? 
7 Australia; ex c. Asiat. Soc., 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, Ksq. 
2. Risella imbricata. 
Littorina imbricata, Gray, Beechey’s Voy., 1839 [sine Hab.]; = Risella 
kielmannseggi, Frauenfeld, 1866, N. Zealund, 
1 Australia; ex c. G. Nevill, Esq. 
. 
