12 CATALOGUE OF PHANEROPNEUMONA. 
nelled, marginate; whorls 4, rather convex, marked with a 
distinct impressed line near the suture, last whorl a little de- 
pressed, shortly descending and disjoined anteriorly ; aperture 
scarcely oblique, circular ; peristome continued, a little angu- 
late above, simple, straight ; the right margin above a little 
arcuate and dilated. Operculum externally deeply concave, 
with about 6 whorls, the margins of which are raised and fur- 
nished with a fringed membrane. Height 5, greatest breadth 13, 
least br. 103 mill. 
Cyclostoma suturale, Sow. in Proc. Z. 8. 1843, p. 29; Thes. p. 91, 
n. 1, t. 23, f. 1,2; Pfr. Ic. p. 109, n. 109, t. 12, f. 10-12. 
Aperostoma suturale, Pfr. in Z. f. Mf. 1847, p. 104. 
Cyclotus suturalis, Gray, Cat. Cyc. p.7,n.8; Pfr. Consp. n. 12 ; 
Mon. p. 24. 
Hab. Demerara (Bainbridge), and Jamaica. 
13. CycLoTUS DUBIOSUS. 
This species differs in one very striking character from C. suturale, 
Sow., it wants the keel next below the suture, in the place of 
which there is a depression of the upper part of the whorls. 
(Ad.) 
Cyclostoma dubiosum, Adams, Contrib. to Conch. n. 9, p. 157. 
Cyclotus? dubiosus, Pfr. Consp. n. 14; Mon. p. 25. 
Hab. Jamaica. 
14. CycLoTus DISTINCTUS. 
Shell discoidal, thin, whitish, with numerous radiating striz and 
less crowded spiral ridges, which are alternatively less raised ; 
spire flat, with the apex scarcely prominent; suture deeply 
indented, channelled ; whorls 35, nearly flat, the last one de- 
pressed (its breadth surpassing its height), disjoied anteriorly ; 
umbilicus broad ; aperture nearly perpendicular, circular; peri- 
stome simple, continued, straight, sharp ; its left margin a little 
expanded. Operculum shelly, furnished with a fringed mem- 
brame. Height 53, greatest breadth 14, least br. 105 mill. 
Cyclostoma distinctum, Sow. Thes. p. 106, n. 47, t. 24, f. 38; Pfr. 
Ic. p. 146, n. 155, t. 20, f. 7-9. 
Cyclostoma orbella (Lam.), Petit, Journ. Conch. 1850, i. p. 48. 
Cyclophorus ? distinctus, Pfr. in Z. f. I, 1847, p. 108; Gray, Cat. 
p. 22, n. 33. 
Cyclotus distinctus, Pfr. Consp. n. 13 ; Mon. p. 24. 
Hab. W. Columbia, Bay de Montija (Cuming), Haiti (Sallé). 
