PTEROCYCLOS. A1 
Obs. 1. Differt a persimili C. Tayloriano spira subturbinata, anfractu 
ultimo descendente, umbilico angustiore, peristomate distincte duplicato, 
tubulo ab apertura remotiore. 
Obs. 2. Conf, Pterocyclos spiracellum Ad. et Reeve. 
II. Pierocyelos Benson. 
Opereulum subcarülagineum, 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 Journ. 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. 
— Som. 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. Soc. 1847. p. 182. 
— Benson in Ann. and Mag. nat. hist. 2d. ser. I. 1848. p. 345. 
-- Gray Catal. Cyclophorid. 1850. p. 11. 
— Pfeiffer iw Zeitschr. f. Malak. 1851. p. 1. 135; Consp. p. 7. 
Spiraculum. Pearson in. Journ. As. Soc. II. 1833. p. 590. 
Steganotoma Troschel in Wiegm. Arch. f. Nat. 1837. I. p. 163. 
— Philippi Abbild. I. 1844. p. 105. 
Cyclostomatis species Lam., Som., Desh., Soul., Petit. etc. 
Myxostoma Trosch. in Zeitschr. f. Malak. 1847. p. 44. 
Species in genere meo sensu cireumscripto enumerandae, in 
sequentes sectiones distribuendae erunt: 
A. Aberrantes: 
l. 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— 10. 
