PTEROCYCLOS. 
41 
O b s. 1. Differ! a persimili C. Tayloriano spira subturbinata, anfractu 
ultimo descendente, umbilico angustiore, peristomate distincte duplicato, 
tubulo ab apertura remotiore. 
Obs. 2. Conf. Ptcrocyclos spiracellum Ad . et Reeve. 
II. Pterocyclos Benson. 
Operculum subcartilagineum , multispirum, spiraliter la- 
mellatum, intus concavum. Testa late umbilicata, subdiscoi- 
dea; peristoma plerumque duplex, internum breve, margine 
supero incisum, externum superne in alam vel rostrum tecti- 
forme dilatatum. 
Pterocyclos Benson in Joura. As. Soc. I. 1832. p. 11. et V. 1836. p. 356. 
— Benson in Zool. Journ. V. N. 20. 1834. p. 462. 
— Gray Syn. Brit. Mus. 1840. p. 133. Ed. 1842. p. 71. 91. 
— Sow. jun. Conch Man. ed II. p. 238. 
— Pfeiffer in Mart, et Chemn. Conch. Ed. nov. I. 19. p. 193. 
Troschel in Zeitschr. f. Malak. 1847. p. 44. 
— Pfeiffer ibid. p. 111. 
— Gray in Proc. Zool. Soe. 1847. p. 182. 
— Benson in Ann. and Mag nat. hist. 2d. ser. I. 1848 p. 345. 
Gray Catal. Cyclophorid. 1850. p. 11. 
— Pfeiffer in Zeitschr. f. Malak. 1851. p. 1 . 135; Consp. p. 7. 
Spira cnlum Pearson in Journ. As. Soc. II. 1833. p. 590. 
Sleyanotoma Troschel in Wiegm. Arch. f. Nat. 1837. I. p. 163. 
— Philippi Abbild. I. 1844. p. 105. 
Cyclostomatis species Lam ., Sow., Desk., Soul., Petit etc. 
Myxostoma Trosch. in Zeitschr. f. Malak. 1847. p. 44. 
Species in genere meo sensu circumscripto enumerandae, in 
secpientes sectiones distribuendae erunt: 
A. Aberrantes: 
1. Peristomate subsimplice . . . §. 1. Nr. 1. 
2. Perist. duplice, operc. planiusculo, 
anfract. extimis lamellatim elevatis 
(Myxostoma Trosch.) . . . . §.2. — 2 — 3. 
B. Genuini, operculo extus alte convexo, 
margine anfractuum lamellatim patente §.3. —4 — 16. 
