GASTEROPODA. 



135 



fissure. Operc. with a broad, membrauous border. W. Indies, Zauzibar, 

 Pacific. 



Modulus, Gray (and nina, Gray) M. tectum, PI. IX., fig. 13. SheD tro- 

 chifonu or naticoid ; porcellanous ; columella perforated ; iimer lip worn or 

 toothed ; operc. horny, many-whirled. Listr., Pliilippines, W. America. 



Fossarus (Adans.) Philippi. F. sulcatus, PI. IX., fig. 12. Syn., pha- 

 sianema. Wood. Shell perforated ; inner lip thin; operc. not spiral. Distr., 

 Medit. Fosdl, 3 sp. JNIiocene — . Brit., Medit. 



Risella, Gray. Lit., mclanostoma, PI. IX., fig. 14. SheU trochiform, 

 \\-ith a flat or concave base ; whirls keeled ; aperture rhombic, dark or varie- 

 gated, operc. pauci-spkal. Distr., N. Zealand. 



Solarium, Lam. Stair-case shell. 



Uii/m., solarium, a dial. 



Syn., architectoma, Boltcn. PhiKppia, Gray. Helicociyptus, D'Orb ? 



Type., S. perspectivum, PL IX., fig. 15. 



Shell orbicular, depressed ; umbilicus wide and deep ; aperture rhombic ; 

 peristome thin ; operculum homy, sub-spii'al. 



The spiral edges of the whirls, seen in the umbilicus, have been fancifully 

 compared to a winding stair-case. 



Diifr., 25 sp. Tropical seas. Medit., E. Africa, India, China, Japan, 

 Australia, Pacific, W. America. 



Fossil, 56 sp. Eocene — . Brit., &c. 26 other sp. (oohtes — chalk,) are 

 pro\-isionally referred to this genus ; the cretaceous sp. are nacreous (v. 

 trochus) . 



Suh-genera. Torinia, Gray. T. cylindracca, operc. conical, 

 multi-spiral, ^vith projecting edges, fig. 82. Living, New Ire- 

 land. Fossil, Eocene. Brit. Pai'is. 



Omalaxis, Desh. (altered to bifrontia) S. bifrons, discoidal, 

 the last whirl disengaged. 6 sp. Eocene, Paris, Brit. 



.'' Orbis, Lea. Discoidal, whirls quadi-ate. Fossil, Eocene, 

 America. 



? PiiOEUS, Montf. Carrier-shell. 



Etym., jjhoreus, a carrier. 



Syn., onustus. Humph., Xenophorus, Fischer. 



Examples, V. conchy liophorus, Born. P. corrugatus, PI. X., fig. 1. 



SJiell trochiform, concave beneath ; whirls flat, with foliaceous 

 or stellated margins, to which shells, stones, &c., are usually 

 afiised ; aperture very oblique, not pearly ; outer lip thin, much 

 produced above, receding far beneath. Operc. horny, imbricated, 

 nucleus external (as m purpura and paludomxis,) with the trans- 

 verse scar seen through it, fig. 83. (Mus. Cuming.) 



* Opeiculum of S. patulura, Lam. -2., from Deshayes. 



