+ 
G CATALOGUE OF PHANEROPNEUMONA. 
yi 
Cyc J. Operculum circular, often externally concave, formed of many 
slowly-enlarging whorls; nucleus central. 
a. Operculum testaceous. 1, Cyclotus; 2, Alyceus; 3, Diplom- 
matina. 
b. Operculum cartilaginous. 4, Pterocyclos. 
c. Operculum horny. 5, Craspedopoma; 6, Aulopoma ; 7, Cyclo- 
phorus; 8, Leptopoma; 9, Megalomastoma; 10, Cataulus; 11, 
Pupinella ; 12, Pupina; 138, Registoma ; 14, Calla. ( 
II. Operculum subcircular ; whorls few, gradually increasing ; 
nucleus subcentral. 
a. Operculum testaceous. 15, Jamaicia; 16, Licina; 17, Choan- 
opoma. 
6. Operculum cartilaginous. 18, Adamsiella. 
III. Operculum oval, or angular ; whorls few, more or less rapidly 
enlarging ; nucleus eccentric. 
a. Operculum testaceous. 19, Lithidion; 20, Otopoma; 21, Cy- 
clostomus ; 22, Tudora; 23, Leonia. 
b. Operculum cartilaginous, covered externally with a thin 
shelly layer. 24, Cistula. 
ce. Operculum simply cartilaginous. 25, Chondropoma. 
d. Operculum double, acuminated within. 26, Pomatias. 
e. Operculum horny. 27, Realia; 28, Omphalotropis; 29, Bour- 
ceria. 
A. Onerculum orbicular, often concave externally, of many ver 
P We Aa Y) y J 
gradually-enlarging whorls, nucleus central. 
a. Operculum thick, formed of two lamina, with a groove on the 
edge between them, the interior horny, the outer layer calcareous, 
the whorls usually furnished with a raised border on the outer 
edge, forming a spiral ridge or fringe. Cyclotina, Gray. 
1. CYCLOTUS. 
Operculum thick, testaceous, outer surface rather concave ; whorls 
numerous ; very gradually enlarging, furnished with a thick- 
ened or raised border on the outeredge. Shell subturbinate, 
depressed, or discoidal; peristome continued or joined by a 
callous margin, simple or double, straight or reflexed. 
Oyclotus, Guild, in Swains. Malac. p. 186, 336 ; Gray, Syn. Br. Mus. 
ed. 1842, p.91; Proc. Zool. Soc. 1847, p. 182; Catal. Cycloph. 
p-5; Herrm. Ind. Gen. Mal. i. p. 350; Pfr. in Z. f. M. 1851, 
p. 182; Consp.p.4; Pneum. Mon. p. 16. 
Aperostoma (part), Zvrosch. in Zeitschr. £. Mal. 1847, p. 44. 
