PTEROCYCLOS.— Plate I. 



Ill this species, lately named by Dr. PfeifFcr, the shell is 

 subglobosely turbinated, with the iinibilicus rather con- 

 tracted, as in P. brevis. Immediately below tiie peri- 

 phery it is encircled with a conspieuous chestnut band, 

 above it the colouring is disposed in promiscuous zigzag 

 splashes. 



Species 3. (Fig. a, h, Mus. Cuming.) 



Ptehocyclos planoebulus. Pk'r. ttstdperampUteraperte 

 unihilicatu., discoided, fidvo-caHaneo thictd et obscure 

 fasciald, anfractibus rotmidatis, ad sutaras lineari-im- 

 pressis, mperne tmnide plicato-corrnyalls, deinde dta- 

 gonaliler malleatis ; aperturd ohliqui; circulari, labro 

 dufdicato, sum paniusciilo. 



The coiled Pteeocyclos. Shell very largely openly 

 umbilicated, discoid, stained and obscurely banded 

 throughout with fulvous chestnut, whorls rounded, 

 linearly impressed at the sutures, tumidly plicately 

 wrinkled round the upper part, then diagonally mal- 

 leated ; aperture obliquely circular, lip duplicate, 

 sinus rather small. 



Cyclostoma planorbidiim , Lamarck, Enc.Meth. pi. 461. f. 3. 

 Cyclolns planorbulus, Swainson. 

 Plei'ocydos planorbulus, Pfeifl'er. 



Hab. Pulo Condore. 



The swollen wrinkles throughout the sutural margin of 

 the whorls show indications of the presence of the auri- 

 cidar sinus, or of the development of some approach to the 

 formation of one, from an earlv stage of growth. 



Species 4. (Fig. a, b, Mus. Cuming.) 



Pterocyclos brevis. Pier, tcstd subainplUer excavato- 

 umbilicatd, solidd, fnlvo-caslaiieo ibwld et obscure fas- 

 ciatd, versus apicem strhjatd, anfraclibus rolundatis, 

 ad suluras impressis et marginutis ; aperturd circulari, 

 labro crasse rejlexo, sinu continuo-producto. 



The short I'terocyclos. Shell rather largely exca- 

 vatcly umbilicated, solid, stained and obscurely banded 

 with fulvous chestnut, streaked towards the apex, 

 whorls rounded, impressed and margined at the su- 

 tures, aperture circular, lip thickly reflected, siiuis 

 continuously produced. 



Liluus brevis, Martyn, Univ. Conch, pi. 38. 

 Turbo PetiveriauHS, Wood. 

 Cyclostoma Petiverianum, Gray. 

 Cyclostoma breve, Pfeiff'er. 

 Myxosloma Petiverianum, Troschel. 

 Cyclophorus brevis, Benson. 



Hab. Pido Condore. 



In this species the sinus is continuously produced, as 

 the shell advances in growth, resting on the body whorl. 

 The circumference of the umbilicus is angularly excavated. 



Species 5. (Fig. a, b, Mus. Cuming.) 



Pterocyclos tenuilabiatus. Pter. lestd perampliler 

 aperte unibilicaid, anyuste discoided, fulvo-castaneo 

 uudiqite imdato-marmoratd, anfractibus rolundatis, 

 subobscure diagonaliter malleatis, dense amiulato- 

 striatis ; aperturd parviusculd obliqud, labro plano-re- 

 flexo, sinu tenue late dilatato. 



The thin-lipped Pterocyclos. Shell very largely 

 openly umbilicated, narrowly discoid, wave-marbled 

 throughout with fulvous chestnut, whorls rounded, 

 somewhat obsciu'ely diagonally malleated, closely 

 ring-striated ; aperture rather small, oblique, lip flatly 

 reflected, sinus thinly broadly dilated. 



Cyclostoma tenuilabiatum, Metcalfe, Pro. Zool. See. 1851, 

 p. 71. 



Hub. Borneo. 



An elegant, narrowly discoid species, in which the sinus, 

 continuous with the outer expanded lip, is thinly broadly 

 dilated, wino-like. 



