STROMBUS. Auct. _Fam._ Alatæ, Lam. Angiostomata, Bl.--_Descr._ Oblong, turrited, rather ventricose, solid; aperture generally lengthened, terminating posteriorly in a short canal, and anteriorly in an emargination or truncated canal; outer lip, when young, thin; when full grown, thickened and expanded, lobed at the spiral extremity, sinuated anteriorly near the caudal canal.--_Obs._ This well known genus includes some species of immense size, commonly called conch shells. Most of the recent species are brought from the Indian Ocean. Very few fossil species are known. The young shells have very much the appearance of cones, the outer lips being thin. There are also several species which do not, even when full grown, thicken their outer lips very considerably. The genus Strombus is distinguished from Rostellaria, by the notch in the outer lip, which in the latter genus is close to the canal. Fig. 406, S. pugilis. STROPHOMENA. Rafinesque. ORTHIS, Dalman. STROPHOSTOMA. Deshayes. A fossil shell, of the family of Colimacea, Lam. in some degree resembling Anostoma, having the aperture turned upwards towards the spire, it is, however, umbilicated, and is said to have an operculum resembling that of Cyclostoma. It is the Ferussina of Grateloup. Fig. 534, 5, 6. STRUTHIOLARIA. Auct. (_Struthio_, an Ostrich.) _Fam._ Canalifera, Lam.--_Descr._ Oblong, turrited, thick; spire turrited, composed of several angulated whorls; aperture oval, sub-quadrate, oblique; outer lip thickened, reflected, advancing in the centre, receding towards the extremities; inner lip thickened, expanded over the columella and part of the body whorl.--_Obs._ This singular genus, consisting of three or four recent species, is named "Pied D'Autruche" by the French, on account of some resemblance in the outer lip to the foot of the Ostrich. From New Zealand. Fig. 391, S. straminea. STYLIFER. Brod. (_Stylus_, a style; _fero_, to bear.)--_Descr._ Thin, pellucid, turbinated; apex a little out of the perpendicular; aperture wide anteriorly, gradually narrowing towards the spiral extremity, where it terminates acutely.--_Obs._ This is a genus of small, transparent shells, found burrowing in the rays of Starfish. There are but two or three species at present known, one of which is elongated like Terebra, the other nearly globular. Fig. 12, S. astericola. West Indies, Gallapagos, and Britain. STYLINA. Flem. STYLIFER, Brod. SUB. (_under._) Used as a prefix and signifying nearly. Thus a bivalve-shell, the valves of which are nearly alike, would be described as _sub_-equivalve. SUB-APLYSIACEA. Bl. The first family of the order Monopleurobranchiata, Bl. containing several genera of Mollusca without shells, and the genus Pleurobranchus.