GASTEROPODA. 2538 
Distribution, Philippines, West America. 
Fossarus (Adans.), Philippi. F. sulcatus, Pl. IX., Fig. 12. 
Synonym, Phasianema, Wood. 
Shell perforated ; inner lip thin; operculum not spiral. 
Distribution, Mediterranean. 
Fossil, 3 species. Miocene—. Britain, Mediterranean. 
Risella, Gray. Lit., melanostoma, Pl. IX., Fig. 14. 
Shell trochiform, with a flat or concave base; whorls keeled 3 
aperture rhombic, dark or variegated, operculum pauci-spiral. 
Distribution, New Zealand. 
Conradia, Adams. Aperture circular. 3 species, Japanese seas. 
Couthouyia, Adams. Shell ovate, with an acute spine; aper- 
ture semi-oyal. 1 species, Japanese seas. 
SOLARIUM, Lam. Stair-case shell. 
Etymology, solariwm, a dial. 
Synonyms, architectoma, Bolten. Philippia, Gray. Helico- 
- eryptus, D’Orbigny ? 
Type, 8. perspectivum, Pl. IX., Fig. 15. 
Shell orbicular, depressed; umbilicus wide and deep; aper- 
ture rhombic ; peristome thin; operculum horny, sub-spiral. 
The spiral edges of the whorls, seen in the umbilicus, have 
been fancifully compared to a winding stair-case. 
Distribution, 25 species. Tropical seas. Mediterranean, Hast 
Africa, India, China, Japan, Australia, Pacific, West America. 
Fossil, 56 species. EHocene—. Britain, &c. 26 other species 
_(oolites—chalk) are provisionally referred to this genus; the 
cretaceous species are nacreous (y. trochus). 
Sub-genera. Torinia, Gray. T. cylindracea, oper- 
culum conical, multi-spiral, with projecting edges, 
Fig. 107. Living, New Ireland. 
Fossil, Eocene. Britain, Paris. 
Bifrontia, Desh. (Omalaxis, Desh.) 8. bifrons, 
discoidal, the last whorl disengaged. 1 recent 
species. Madeira. Fig. 107.* 
Fossil, 6 species. Eocene. Paris, Britain. 
? Orbis, Lea. Discoidal, whorls quadrate. 
Fossil, Eocene. America. 
Discohelix (calculiformis) Dunker, 1851. JZias, Gottingen. 
This name was proposed for the depressed Huomphali of the 
Lower Oolites, of which there are several species in Normandy 
and England. 
* Operculum of 8 patulum, Lam, 3, from Deshayes. 
