SPHÆRULACEA. Lam. The fourth family of Cephalopoda, Lam. described as multilocular, globular, sphærical, or oval, with the whorls enveloping each other; some of them have a particular internal cavity, and are composed of a series of elongated, straight and contiguous chambers which altogether form a covering for the internal cavity. This family contains the genera Miliola, Gyrogona and Melonia. SPHÆRULITES. Lam. (_Sphæra_, a sphere.) _Fam._ Rudistes, Lam. and Bl.--_Descr._ Orbicular, inequivalve, irregularly foliated outside; lower valve cup-shaped, depressed; upper valve nearly flat, like an operculum.--_Obs._ These fossils are not regarded as shells by all conchologists. S. foliacea, Fig. 193. SPHINCTERULUS. Montf. LENTICULINA, Bl. A genus of microscopic Foraminifera. SPINES. (_Spina_, a thorn.) Thin, pointed spikes. SPINOSE. (Spinosus.) Having spines or elevated points, as Neritina spinosa. Fig. 325. SPIRAL. (_Spira_, a spire.) Revolving outwards from a central apex or nucleus, like the spring of a watch. A shell or an operculum, may be spiral, without being produced into a pyramid. Bands of colour, striæ, grooves, &c. commencing from the nucleus and following the volutions of the shell, are described by the above word. SPIRAMILLA. Bl. A genus of Serpulacea, differing from other Serpulæ principally in the characters of the animal. SPIRATELLA. Bl. LIMACINEA, Lam. Fig. 224. SPIRE. (_Spira._) The cone or pyramid produced in a non-symmetrical univalve by its oblique revolution downwards from the apex or nucleus. The spire, in descriptions, includes all the volutions above the aperture. See Introduction. SPIRIFER. Sow. (_Spira_, a spire; _fero_, to bear.) _Order_, Brachiopoda, Lam.--_Descr._ Transverse, equilateral; hinge linear, straight, widely extended on both sides of the umbones, which are separated by a flat area in the upper and larger valve; this area is divided in the centre by a triangular pit for the passage of the byssus; interior with two spirally convolute appendages.--_Obs._ This genus, which is only known in a fossil state, is distinguished from Terebratula externally, by the flat area in one valve, internally, by the singular spiral process from which the above name is derived. Fig. 214, 215. Most of the species belong to the mountain or carboniferous limestone. SPIROGLYPHUS. Daud. A genus consisting of a species of Serpula _Auct._ which makes a groove for itself in the surface of shells. Serpula spirorbis, var. Dillwyn. Fig. 8. SPIROLINA. Lam. A genus of microscopic Foraminifera. SPIROLOCULINA. D'Orb. A genus of microscopic Foraminifera.