CYCLOPHORIDZ. 5 
1, Cyclostoma ; 2, Pomatias; 3, Aulopoma (Hofmeisteri) ; 4, Apero- 
stoma (volvulus) ; 5, Zropidophora (Cuvieranum); 6, Fareimen 
(flavulum) ; 7, MJyxostoma (Petiverianum) ; 8, Pterocyclos Ste- 
ganostoma. 
Dr. Pfeiffer, in the same volume, p. 47, proposes to add to these, 
1, Leptopoma ; 2, Choanopoma ; 3, Craspedopoma ; and at p. 104, 
gives a list of the specimens of the family, arranged under the 
genera which had then been established. 
In 1848, M. L. Partiot (Mém. sur les Cyclostomes, Toulouse, 8vo), 
divides the family thus, with the types :— 
1, Acme (fusca) ; 2, Pomatias ; 3, Hricia (aurantium) ; 4, Gastro- 
donia (fimbriatulum) ; 5, Cyclophorus ; 6, Annularia; 7, Ste- 
ganostoma. Characterized by the form of the shell, they con- 
sist of most Incongruous species. 
In 1850, Dr. Gray (List of Cyclophoride, in Brit. Mus.) divides 
the family thus :— 
A. Operculum orbicular, often concave externally, of many very 
gradually-enlarging whorls ; nucleus central. 
a. Operculum thick, formed of two lamina, with a groove on the 
edge between them; the outer layer calcareous, usually 
furnished with a raised border in the outer edge, forming a 
spiral ridge or fringe. 1, Cyclotus (Poteria) ; 2, Pterocyclos ; 
3, Craspedopoma (Bolania). 
. Operculum horny, thin, without any external calcareous layer. 
Shell conical, or depressed ; last whorl rounded, without any 
groove or ridge round the front of the axis. 4, Azdlo- 
poma ; 5, Myzostoma; 6, Cyclophorus; 7, Leptopoma ; 8, Aly- 
CeUS. 
. Operculum horny, thin, many-whorled. Shell oblong, elon- 
gate, last whorl with a fold or spiral ridge on the inner side, 
in front of the axis, sometimes forming a groove in the outer 
lip. 9, Farcimen ; 10, Hlectrina ; 11, Megalomastoma ; 12, Re- 
gistoma ; 13, Pupina ; 14, Pupinella ; 15, Callia. 
i] 
aq 
B. Operculum ovate, of a few more or less rapidly-enlarging 
whorls ; nucleus eccentric. 
a, Operculum thick, with an externally shelly coat. 16, Leonia ; 
17, Lithidion ; 18, Otopoma ; 19, Trochidophora ; 20, Cyclo- 
stomus; 21, Tudora; 22, Choanopoma; 238, Diplommatina ; 
24, Chondropoma ; 25, Cistula; 26, Licina. 
6. Operculum thin, few whorls, front of last whorl rounded. 
27, Pomatias ; 28, Realia ; 29, Ferussina. 
1851, Dr. Pfeiffer, in his Conspectus Cyclostomaceorum, divides 
the family thus :— 
B2 
