CLASS IV 



GASTROPODA 



551 



and body whorl often retaining tiaces of apertures at earlier stages. Veiy abimdant 

 in Jura and Cretaceons. 



Subgenera : Dicroloma Gabb ; Anchura Conrad (Fig. 987). 

 Cretaceous. Diempterus Piette. Jura. 



Jura and 



Fig. 985, 



Alaria myurus Deslongch. 

 Lower Oolite ; Bayeux, Cal- 



FiG. 987. 



Fig. 



Alaria armata Morris 



and Lyc. Great Oolite; Alaria (Anchura) cari- 



Minchinhanipton, Eng- nata Mant. Gault ; 



land. . Folkestone, England. 



Fig. 988. 



Spinigera semicarinata 

 (Goldfuss). Callovian ; 

 Montreuil - Bellay, 

 Maine-et-Loire. 



Spinigera d'Orb. (Fig, 

 rows of spines. Jura. 



Aporrhais Da Costa {Ghenopus Phil.) (Figs. 

 989-991). Like Alaria, but niargins of aperture 

 elongated posteriorly in a canal, which remains 

 either attached to tbe spire, or extends free froiu 

 the sanie. Outer lip expanded, digitated or lobed. 

 Jura to Recent. 



Wliorls keeled and ornamented with two opposite 



Subgenera : AUpes Conrad ; ArrJioges, Tessarolax^ 

 Helicaulax Gabb ; Ceratosi'phon Gill ; Cuphoselenus, 

 Malaptera Piette ; Pterocerella Meek ; Dimorphosoma 

 St. Gardner (Fig. 990) ; Lispodesthes White (Fig. 

 991). Jura and Cretaceous. 



Fi(i. 989. 



Aporrhais tridaciylus A. Braun. Oligo- 

 cene ; Hackenheim, near Creuznacli. 



Fk;. 990, 



Aporrhais (Dimor- 

 phosoma) calcarata 

 Sowb. Upper 

 Greensand ; Black - 

 down, England. 



Fig. 991. 



Aporrhais (Lispodesthes) rettssi Geinitz 

 var. viegaloptera Reuss. Pläner ; Postelberg, 

 Boheinia. 



Family 19. Strombidae d'Orbigny. 



Shell conical, turreted or fitsiform, with acuminate spire. Aperture canaliculate ; 

 outer lip often expanded, anteriorly with an emargination. Operculum horny. Jura 

 to Recent. 



Although the shells of this family are excessively variable, the soft parts of the 

 animals exhibit great uniformity of structure. 



