PTEROCYCLOS.— Plate IV. 



also curiously pushed from its spire of convolution on 

 arriving at maturity, in consequence of the sinus, cha- 

 racteristic of this genus, being developed into a tube. 



Species 31. (Pig. a, b, Mus. Cuming.) 



Pterocyclos Hocsei. Pter. testd sithainpliicr aperte 

 umhil'watd, dbscolded, albidd, sti-igis mir/ustis fulves- 

 cenie-fuscis pictd, anfraclibus ad siituras impressis et 

 marginaiis, deinde rotimdatis, dense tenuistriatis, an- 

 fractu ultimo solvto ; nperturd circulari, labro tenue 

 expanso, siitu in tubulum angndum eiongatum fvoduclo. 



House's Pterocyclos. Shell rather largely openly 

 umbilicated, discoid, wliitish, painted with narrow 

 fulvous-brown angular streaks, whorls impressed and 

 margined at the sutures, then rounded, closely finely 

 striated, last whorl uncoiled ; aperture circular, lip 

 tliinly expanded, sinus produced into a narrow 

 elongated tube. 



Cyclostoma Housei, Haines, Ann. Lye. New York, vol. vi. 

 p. 157. pi. 5. f. 12 to 15. 

 Rhiosloma Housei, Benson. 



Hab. Siam ; House. 



A more slenderly convoluted species than the preceding 

 with the tube rather narrower and longer. 



Species 22. (Mus. Cuniiug.) 



Pterocyclos Cochinchinensis. Pter. tesld sublale 

 aperte mnbilicatd, discoided, sub epidermide fulvd alba, 

 atifradibiis rotnnduti.s, undique tenuistriatis, an- 

 fractu ultimo subsolnto ; aperturd circulari, labro 

 siinplici, sinu in tubulum parmim productu. 



The Cochin-China Pterocyclos. Shell rather broadly 

 openly umbilicated, discoid, white, beneath a fidvous 

 epidermis, whorls rounded, finely striated throughout, 

 last whorl slightly uncoiled ; aperture circulai-, lip 

 simple, sinus produced into a small tube. 



Cyclostoma Cochinchinense, Pfeiffer, Pro. Zool. Soc. 1856, 

 p. 337. 

 Opisthoporus Cochiuchiiiensis, Pfeitfer. 



Hab. Cochin-China. 



Better specimens than are at present known of this 

 species are required to ascertain its colouring. The shell 

 here figured is entirely denuded of its epidermis. 



