BY THE REV. J. E. TENISON-WOODS. 
1061 
22. Opisthoporus, Benson. 
Zeitschr. f. Malak. 1851, p. 8 ; Pfr. Mon. Pneumon. Viv. 
Suppl. 111. p. 41 ; Zeitschr. f. Malak. 1851, p. 8 ; Pfr. Mon. 
Pneumon. Yiv. Suppl. I. p. 25, 11. p. 36. 
Shell depressed, oi’kiculai’, largely uinbilicate ; aperture double, 
with the external parts spread out ; suture behind the opening 
and furnished with a little open tube ; operculum calcareous, 
circular, rather thick, concave at both sides, multispiral, double ; 
the internal side covered with a horny periostraca, the external 
calcareous and rough ; columella margin concave. 
Opisthoporus solutus, Stol. Jour. As. Soc. Beng. XLl. 
1872, p. 266, ph 10, figs. 8-10; Pfr. Mon. Pneumon. Suppl. 111. 
1876, p. 44; G. Xevill, Handl. Moll. Ind. Mus. 1878, p. 263 ; 
H. Crosse, Jour. Conch. XXVll. 1879, p. 337. 
Bukit Pondok ; Penang. 
0. PENANGENSis, Stol. l.c. 1872, p. 265, pi. 10, fig. 7 ; Pfr. 
INIon. Pneumon. Suppl. 111. 1876, p. 43 ; G. Nevill, Handl. 
1878, p. 263 ; H. Crosse, Jour. Conch. XXVll. 1879, p. 338. 
Bukit Pondok ; Penang. 
O. JAVANUS, Pfr. Malak. Bl. Vll. 1860, p. 215, pi. 3, 
figs. 8-10; Mon. Pneumon. Suppl. 11. 1865, p. 37. 
Nungnang, Java. 
O. SUMATRANUS, von Mart. Monatsber. Berk Ak. 25 Feb. 
1864 ; Pfr. Mon. Pneumon. Suppl. 11. 1865, p. 37. 
Sumatra. 
(?) O. spiNiPERUS (Cyclostoma), Morelet, = Cyclostoma syini- 
fcrum, Morelet, Jour. Conch. IX. 1861, [>. \11 = Opisthoporus 
spinifer'us, von Mart. Ostas. Zool. 11. p. 113; Pfr. Mon. Pneu- 
mon. Sui)j)l. 111. p. 41. 
Borneo. 
O. PKRTU8U8 (Cyclostoma), Morelet; Issel, Moll. Born. p. 75; 
Pfr. Mon. Pneumon. Suppl. 111. p. = Cyclostoma pertusuviy 
Morelet, Jour. Concli. IX. 1861, p. 177. 
Borneo. 
