244 ARCniTECTONICID^. 



ties of the animal become better known we prefer to 

 keep the genus here. 



Species of PhiUppia. 

 hybrida, Linn. lutea, Lavi. 



Genus OMALAXIS, Deshayes. 



Operculum circular, elevated, many-whorled. 



Shell orbicular, discoidal, widely umbilicated, umbi- 

 licus keeled ; whorls numerous, on the same plane, the 

 last detached from the others, the periphery with one 

 or two keels; aperture small, usually triangular; outer 

 lip acute. 



Syn. Bifrontia, Desk. Omalaxon, Agass. Schizos- 

 toma, Bronn.^ not Lea. Euomphalus, J. Sow. 



Ex. O. Zanclea, PhiUppi, pi. 25, fig. 9, 9, a. Opercu- 

 lum, O. Zanclea, fig. 9, h. 



Living examples of this genus, only known before in a 

 fossil state, have been recently dredged oif the coast of 

 Madeira by Mr. Mac-Andrew, who states that the animal 

 is nearly pellucid. 



Genus DISCOHELIX, Dunker. 



Shell discoidal, greatly depressed, nearly foliaceous, 

 whorls very numerous, on the same plane, rounded or 

 carinated at the periphery, the last not detached; aper- 

 ture wide, transverse. 



Syii. Orbis, Lea, not Schrot. or Lacep. 



Ex. D. foliacea, Philippi, pi. 25, fig. 10, 10, a. 



