SOLARIIDA. 217 
a strong revolving plate inside, nearly midway between the 
umbilical and outer margin on the base. Cretaceous; Miss. 
and Alabama; described from a cast. X. umbilicata, Tuomey. 
Famity SOLARIID. 
Shell orbicular, depressed or trochiform; aperture generally 
angular; umbilicus usually wide and deep. Operculum corneous, 
spiral. 
The animal has folded tentacles, with the suture below; eyes 
sessile on the upper surface of their bases; gill-cavity divided 
by a longitudinal fold; proboscis retractile. 
The shells are not pearly like Trochus—which many of them 
resemble. They are numerously represented in fossil deposits, 
commencing in the Trias, and reaching their maximum in the 
Tertiary. There are not many living species. Dentition 
(xii, 39, 40). 
Sovarium, Lam. 
Etym.—Solarium, a dial. 
Syn.—Architectonica, Bolten. Solariorbis, Conrad. 
Distr.—25 sp. Tropical; world-wide. Fossil, more numerous. 
Commencing with the Eocene. 8S. perspectivum, Linn. (Ixvi, 34). 
Shell depressed conic, angular at the periphery ; aperture sub- 
quadrangular, lip simple; umbilicus wide, spiral, its margins 
crenulated. Operculum horny, subspiral. 
TORINIA, Gray. (Heliacus, d’Orb.) Shell orbicular, elevated, 
granulated, last whorl rounded; moderately but profoundly 
umbilicated. Operculum conically elevated, of numerous volu- 
tions, which are margined by projecting edges cork-screw 
fashion. S. variegatum, Lam. (1xvi, 35). 
Distinguished from Solarium by its spirally elevated oper- 
culum, and by the rounded periphery of the last whorl. They 
affect deep water, and are very shy and sensitive when under 
observation. 
PHILIPPIA, Gray. (Disculus, Desh.) Shell smooth, subconic ; 
umbilicus with crenulated margins. Operculum flattened,whorls 
numerous. S&S. dutewm, Lam. (lxvi, 36). 
Gyriscus, Tiberi. Shell turbinated, conic-turriculated, um- 
bilicated, rather obtuse, the summit enveloped. Whorls rounded, 
transversely sculptured. Aperture subcircular, the simple 
margins united by a callous deposit; columellar lip reflected. 
Operculum corneous, multispiral externally, furnished internally 
with a central styliform projection. S. Jeffreysianum, Tiberi 
(Ixv, 5,6). Mediterranean. 
FLUXINA, Dall. Shell porcellanous, depressed conical, umbili- 
cate, strongly carinate, with a stout umbilical rib, above which 
the pillar is thin and emarginate ; from the umbilical rib to the 
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