SOLARIID^. 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. umhilicata^ Tuomey. 



Family 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 manj'^ living species. Dentition 

 (xii,39, 40). 



Solarium, Lam. 



Etym. — Solarium,^ a dial. 



Syn. — Architectonica, Bolten. Solariorbis, Conrad. 



Distr. — 25 sp. Tropical ; world-wide. Fossil, more numerous. 

 Commencing with the Eocene. S. perspectivum, Linn. (Ixvi, 34). 



Shell depressed conic, angular at the periphery ; aperture sub- 

 quadrangular, lip simple; umbilicus wide, spiral, its margins 

 erenulated. Operculum horny, subspiral. 



TORiNiA, Gray. (Heliacus, d'Orb.) Shell orbicular, elevated, 

 granulated, last whorl rounded ; moderately but profoundly 

 umbilicated. Operculum conicall}^ elevated, of numerous volu- 

 tions, which are margined by projecting edges cork-screw 

 fashion. S. variegatum, Lam. (Ixvi, 35). 



Distinguished from Solarium by its spirally elevated oper- 

 culum, and b}^ the rounded periphery of the last whorl. They 

 aifect deep water, and are very shy and sensitive when under 

 observation. 



PHiLiPPiA, Gray. (Disculus, Desh. ) Shell smooth, subconic ; 

 umbilicus with erenulated margins. Operculum flattened, whorls 

 numerous. S. luteum, Lam. (Ixvi, 36). 



GYRiscus, Tiberi. Shell turbinated, conic-turriculated, um- 

 bilicated, rather obtuse, the summit enveloped. Whorls rounded, 

 transversel}^ sculptured. Aperture subcircular, the simple 

 margins united by a callous deposit ; columellar lip reflected. 

 Operculum corneous, maltispiral externally, furnished internally 

 with a central styliform projection. S. Jeffrey sianum, Tiberi 

 (Ixv, 5, 6). Mediterranean. 



PLUXiNA, 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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