1062 
MALAYSIAN LAND AND FRESHWATER MOLLUSCA. 
23. Pterocyclos, Benson. 
Jour. Roy. As. Soc. I. 1832 and V. 1836 ; Zoological Journ. V. 
No. 20, p. 462. 
Shell svib-discoid, lai’gely umbilicate ; aperture circular, the 
external layer overlapping the inner and dilated posteriorly with 
a distinct groove at the suture ; operculum thick, composed of 
several spiral calcareous layers externally concave and horny 
within. 
A small genus chai acteristic of the Indian region. 
Pterocyclos albersi, Pfr. Zeitschr. f. Malak. 1847, p. 151 ; 
Ohemn. 2nd edit. Cyclostoma, p. 197, pi. 28, figs. 1-5; Pfr. IVJon. 
Pueumon. p. 45. 
Perak ; Kinta Valley (!), Selama (!). 
Pt. brevis (Lituus), Marty n, = Lituus brevis, Marty n, Fig. of 
non-described shells, pi. 28c; Ed. Chenu (Bibl. Conch. II.) p. 21, 
pi. 8, fig. 2 —Turbo petiverianus, Wood, Suppl. pi. 6. fig. 2 = 
G yclostonia petiverianum. Gray in Wood’s Suppl. p. 36 = Cyclos. 
toma breve, Pfr. in Chemn. 2nd edit. No. 180, p. 166, pi. 24, 
figs. 1-2 = Myocostoma petiverianum, Trosch. in Zeitschr. f. Malak. 
= Pterocyclos brevis, Pfr. Zeitschr. f. Malak. 1851, 
p. 9 ; Consp. No. 46 ; Mon. Pneumon. p. 42. 
India ; Pulo Condor. 
Pt. planorbulus, Lamarck, = Cornu venatorimn, Chemn. Cab. 
IX. p. 104, pi. 127, figs. 1132-33 (^) = Cyclostoma planorbula, 
Lamarck, Encyclop. INIeth. pi. 461, fig. 3— Cyclotus planorbulus, 
Swains. Malacol. p. 336 = Pterocyclos planorbulus, Pfr. Consp. 
No. 47 ; Mon. Pneumon. p. 43. 
Java (?) ; Borneo (?). 
Pt. tenuilabiatus. Mete. ; Pfr. Mon. Pneumon. p. 45 = 
Cyclostoma tenuilabiatum, Mete. Proc. Zool. Soc. 1851. 
Borneo. 
Pt. blandi, Benson, Ann. and Magaz. VIII. 1851, Aug. pi. 5, 
fig. 1 ; Pfr. Mon. Pneumon. p. 49. 
Pulo Susson. 
