460 



MOLLUSGA 



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- 



Fio. 880. 

 Cyclostoma bi- 

 sulcatum, Zieten. 

 Miocene ; Ermin- 

 gen, near Ulm, 

 Wurtemberg. 



FIG. SSI. 



Pomatias labellum, 

 Thomas sp. Helix 

 Beds (Upper Oligo- 

 cene) ; Hochheim, 

 near Wiesbaden. 



FIG. 882. 



Cydotus exaratus, Sandb. 

 Upper Eocene ; Pugnello, 

 'Italy. Shell and operculum 

 (after Sandberger). 



Strophostoma anom- 

 phala, Capellini. Oli- 

 gocene ; Arnegg, near 

 Ulm, Wurtemberg. 



Operculum horny. Cretaceous to 



stome with thick margins ; outer lip reflected. 

 Recent. M. mumia, Lam. sp. 



Pomatias, Studer (Fig. 881). Turreted, transversely striated, with reflected 

 margins and calcareous operculum. Tertiary to Recent ; palaearctic. 



Leptopoma, Pfeiff. ; Cyclophorus, Montf. ; Craspedopoma, 

 Pfeiff. ; Cydotus, 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. 



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, 

 cap-shaped, concentrically striated or 

 FIG. 886. furrowed, with slightly incurved 



elegans, Barr. apex, which latter is distantly situated 



Capulus hitngaricus, Linn, 

 sp. Pliocene ; Tuscany. 



. , . 



BoheS eE);LOChk W ' posteriorly. Lower Cambrian. 



FIG. 



Capulus rugosus, Sowb. sp. 

 Great Oolite ; Langrune, 

 Calvados. 1/1- ^^1..^.. 



Capulus, Moritf. (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 - r 

 internally with a horseshoe-shaped muscular itttjHfession. Exceedingly abundant from 

 the Cambrian to Carboniferous, but rather sparse from the Trias onward. 



Orthonychia, Hall (Igoceras, Hall), (Fig. 886). Shell conical, straight, or slightly 

 curved, often plicated. Apex but faintly spiral. Silurian to Carboniferous. 



