460 MOLLUSCA SUB-KINGDOM VI- 
of these are tropical. Fossil forms are found in fresh-water deposits as old as the 
Middle Cretaceous. 
Cyclostoma, Lam. (Fig. 880).  Turbinate, with calcareous spiral operculum. 
Tertiary and Recent. 
Otopoma, Tudora, Gray. Tertiary and Recent. 
Megalomostoma, Guild. Turbinate to chrysalis-shaped, usually smooth. Peri- 

Fic. 880. Fic. S81. 
Cyclostoma  bi- Pomatias labellum, - Fig. 882. Fic, 883. 
sulcatum, Zieten. Thomas sp. Helix Cyclotus exaratus, Sandb. Strophostoma anom- 
Miocene ; Ermin- Beds (Upper Oligo- Upper Eocene ; Pugnello, phala, Capellini. Oli- 
gen, near Ulm, cene); Hochheim, Italy. Shell and operculum gocene; Arnegg, near 
Wurtemberg. near Wiesbaden. (after Sandberger). Ulm, Wurtemberg. 
stome with thick margins; outer lip reflected. Operculum horny. Cretaceous to 
Recent. M. mumia, Lam. sp. 
Pomatias, Studer (Fig. 881). Turreted, transversely striated, with reflected 
margins and calcareous operculum. Tertiary to Recent ; palaearctic. 
Leptopoma, Pfeift.; Cyclophorus, Montf.; Craspedopoma, 
Pfeiff. ; Cyclotus, Guilding (Fig. 882), etc. Upper Cretaceous. 
These genera are considered to form a distinct family, Cyclo- 
phoridae. Strophostoma, Desh. (Fig. 883) ; Upper Cretaceous 
to Miocene. 
Family 4. Capulidae. Cuvier. 
Shell cup-, cap-shaped, or oval, 
irregular, with spirally twisted apex ; 
in some cases the shell is composed of 
several depressed whorls. Body whorl 
very large; aperture wide ; operculum 
absent. Marine. Cambrian to Recent. 

Fic. 884. 
Capulus hungarieus, Linn. 
sp. Pliocene; Tuscany. 
Various genera belonging here 
are stationary, remaining throughout 
nearly the whole of their existence 
attached to some foreign body, to 
which they gradually become accom- 
modated in form. 
Stenotheca, Salter. Shell small, 
‘ap-shaped, concentrically striated or 

Fic. 885. Fic. 886. furrowed, with slightly incurved 
Capulus rugosus, Sowb. sp. Orthonyghia elegans, Barr. APexX, which latter is distantly situated 
Great Oolite ;  Langrune, Silurian (Htage E); Lochkow, posteriorly. Lower Cambrian. 
Calvados. 1/;. Bohemia. : 
Capulus, Montf. (Pileopsis, Lam. ; 
Brocchia, Bronn), (Figs. 884, 885). Irregularly conical or cap-shaped ; apex greatly dis- 
placed backward, more or less spirally inrolled. Aperture wide, rounded or irregular ; 
internally with a horseshoe-shaped muscular impression. Exceedingly abundant from 
the Cambrian to Carboniferous, but rather sparse from the Trias onward. 
) Bp 
Orthonychia, Hall (Igoceras, Hall), (Fig. 886). Shell conical, straight, or slightly 
y ’ ‘ b b te) b] 5 ’ ” 
curved, often plicated. Apex but faintly spiral. Silurian to Carboniferous. 
