448 



MOLLUSCA 



SUB-KINGDOM VI 



round, ornamented with raised longitudinal keels. Operculum extremely thick, flat 

 internally, conical externally, multispiral. Ordovician to Carboniferous; especially 

 abundant in Silurian. 



Cyclonema, Hall (Fig. 818). Turbinate ; whorls inflated and ornamented with 



FIG. 818. 



Cyclonttnci bilix, 

 Conrad. Ordo- 

 vician ; Cincinnati, 

 Ohio. 



FIG. 819. 



Astmlium(Bolma)rugomm, Linn. Pliocene; 

 Plena, Tuscany. Shell and opereulum. 



FIG. 820. 



Astralium, (U vanilla) Damon, 

 Laube. Keuper ; St. Cassian, 

 Tyrol. 



fine spiral striae. Aperture rounded, peristome discontinuous. Operculum conical, 

 flat internally, externally with spiral flutiiigs. Ordovician to Devonian. 



Astralium, Link. (Figs. 819, 820). Turbinate; whorls 

 rough, often spinose, and usually keeled. Aperture depressed, 

 with disconnected margin. Base more or less flattened ; 

 opereulum calcareous, thick, flat internally, 

 spirally coiled, and with very eccentric 

 nucleus. Trias to Recent. 



Sub-genera : JBolma, Risso (Fig. 819) ; Pachy- 

 poma, Lithopoma, Uvanilla (Fig. 820), Guil- 

 fordia, Gray ; Calcar, Montfort, etc. 



FIG. 821. 



Turbo (Ninella) Parkinsoni, 

 Bast. Oligocene ; Dax, near 

 Bordeaux. 



FIG. 822. 



Collonia modesta, 

 Fuchs. Oligocene ; 



Turbo, Linn. (Fig. 821). 



. 



Monte Grumi, near conical ; aperture nearly circular. 

 Castel Gomberto, 



Turbinate to 

 Oper- 



flat internally, extern- 

 ally convex, multispiral, with sub -central nucleus. Silurian (?) 

 to Recent. 



Sub -genera : Sarmaticits, Ninella (Fig. 821) ; Modelia, Callopoma, 

 Gray ; Senectus, Humphr. ; Batillus, Schum., etc. 



Collonia, Gray (Fig. 822). Like Turbo, but opereulum with 

 thin calcareous layer disposed in a spiral rib. Eocene to Recent. 



Family 8. Phasianellidae. Troschel. 



Shell elongated, oval, thin, smooth, lustrous, porcellanous, not 

 nacreous internally, without umbilicus. Body whorl large, with 

 oval aperture. Operculum calcareous, convex externally. Devonian 

 to Recent. 



FiG. 823. 



Phosianella Gosauica, 

 Zekeli. Turoniau ; 

 Gosati, Austria. 



Phasianella, Lam. (Phasianus, Montf.), (Fig. 823). With 

 the characters of the family. Cretaceous to Recent ; perhaps also Palaeozoic. 



