18 CATALOGUE OF PHANEROPNEUMONA. 
flesh-coloured inside; peristome simple, with the margins almost 
contiguous, upper margin sinuate, a little expanded ; columellar 
margin shortly reflected. Opere. nearly flat, with the margins 
of the whorls sharply raised. Height 8, greatest breadth 17, 
least br. 13$ mill. 
Cyclostoma subdiscoideum, Sow. Thes. Suppl. n. 184, p. 161%, 
t. 31, B. f. 304, 305; Pfr. Ic. n. 325, t. 41, f. 33, 34. 
Cyclostoma rusticum, Pfr. in Proc. Zool. Soc. 1851. 
Cyclotus Pfeifferi, Gray, Cat. Cycl. p. 9, n. 20 (not described). 
Cyclotus subdiscoideus, Pfr. Consp. n. 26; Mon. p. 31, 415. 
Cyclostoma aratum, Bens. in Ann. and Mag. New sey. viii. p. 190. 
Cyclotus aratus, Pfr. Consp. n. 27; Mon. p. 31. 
Hab. East India, the province Northern Cireass. (Jerdon). 
98. CycLOTUS ORBELLUS. B. M. 
Shell nearly discoidal, thin, diaphanous, pale fulvous orash-coloured, 
with sharp spiral ridges, which are distant above, more crowded 
and smaller beneath; spire flat, with the apex prominent, nipple- 
shaped; suture broadly channelled; whorls 45, moderately con- 
vex, the last one cylindrical, deflected anteriorly; umbilicus 
very large; aperture very oblique, nearly circular; peristome 
simple, sharp, with the margins approaching each other; right 
margin a little expanded, crenulate ; basal margin reflected. 
Operc.? Height 55, greatest breadth 14, least br. 11 mill. 
Cyclostoma orbella, Lam. Hist. vi. p. 148, n. 23, ed. Desh. viii. 
p. 360, n. 22; Delesf. recueil, t. 29, f.13; Sow. Thes. nu. 7, p. 93, 
t. 23, £.6%*, 6**; Chemn. Ill. Conch. Livr. 73, t. 1, £13; Pfr. 
Ic. n. 154, p. 145, t. 20, £. 4—6. 
Cyclostoma variabile, Mer. ISS. fide, Mus. Cuming. 
Cyclostoma Lamarckii, Petit, in Journ. Conch. 1. p. 41. 
Cyclophorus ? orbellus, Pfr. in Z. f. Mf, 1847, p. 108. 
Cyclotus? orbellus, Gray, Cat. Cycl. p. 9, n. 21; Pfr. Consp. n. 28 ; 
Mon. p. 32, 8? With the spire a little more raised, and the 
basal ridges more distinct ; operculum typical of Cyclotus. 
Cyclostoma orbella var.? Pfr. Ic. t. 41, f. 26, 27. 
Hab. Madagascar? (Ferussac) ; the variety (?) from Guadaloupe. 
99, CycLoTuUS ? DIATRETUS. 
Shell planorboid, whitish-horn-coloured, angular, with distant ribs 
on the upper side, which are in the intervals crossed by longi- 
tudinal strie; umbilicus broad; spire flattened; whorls 4, 
cylindrical, rapidly increasing, shelving near the suture; aper- 
ture circular; peristome simple. Height 3, breadth 3 inch. (g.) 
