1062 MALAYSIAN LAND AND FRESHWATER MOLLUSCA, 



23. Pterocyclos, Benson. 



Jour. Roy. As. See. I. 1832 and V. 1836 ; Zoological Journ. V. 

 No. 20, p. 462. 



Shell sub-discoid, largely 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 characteristic of the Indian region. 



PTBROcycLOS ALBERSi, Pfr. Zeitschr. f. Malak. 1847, p. 151 ; 

 Cliemn. 2nd edit. Cyclostoma, p. 197, pi. 28, figs. 1-5; Pfr. JVlon. 

 Pneumon. p. 45. 



Perak ; Kinta Valley (!), Selama (!). 



Pt. brevis (Lituus), Martyn, = Lituus brevis, Martyn, 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 ^ 

 Cyclostoma petiverianum, Gi'ay in Wood's Suppl. p. 36 = Cyclos. 

 toma hreve, Pfr. in Chemn. 2nd edit. No. 180, p. 166, pi. 24, 

 figs. 1-2 ^ Myxostoma petiverianum, Trosch. in Zeitschr. f. Malak. 

 184:7, \x ii =: Pterocyclos brevis, Pfr. Zeitschr. f. Malak. 1851, 

 p. 9 ; Consp. No. 46 ; Mon. Pneumon. p. 42. 



India ; Pulo Condor. 



Pt. planorbulus, Lamarck, = Cornu veuatorium, Chemn. Cab. 

 IX. p. 104, pi. 127, figs, 1132-33 (1) = Cyclostoma j)lanorhula, 

 Lamarck, Encyclop. IMeth. pi. 461, fig. 3= Cyclotus planorbulus, 

 Swains. Malacol. p. 336 ^ Pterocyclos pla7iorbulus, Pfr. Consp. 

 No. 47 ; Mon. Pneumon. p. 43. 



Java (?) ; Borneo (1). 



Pt. tenuilabiatus. Mete. ; Pfr. Mon. Pneumon. p. 45 ^ 

 Cyclostoma tenuilabiatum, Mete. Proc. Zool. Soc. 1851. 



Bo)-neo. 



Pt. blandi, Benson, Ann. and Magaz. VIII. 1851, Aug. pi. 5, 

 fig. 1 ; Pfr. Mon. Pneumon. p. 49. 



Pulo Susson. 



