ROSTRATED. (From _rostrum_, a beak.) Having one or more protruding points, as Tellina rostrata. ROTALIA. Lam. A genus of microscopic Foraminifera. The same as Rotalites of De Montfort. ROTELLA. Lam. (_A little wheel._) _Fam._ Turbinacea, Lam.--_Descr._ Orbicular, generally smooth, shining; spire conical, depressed, short; aperture subtrigonal; outer lip thin, angulated near the centre; inner lip spread over the surface of the whorls, forming a thickened disc. Operculum horny, orbicular, spiral, with numerous whorls.--_Obs._ The pretty little shells thus described are found in seas of tropical climates. They are distinguished from other genera of the family by their lenticular form and the orbicular callosity of the under surface. Fig. 357, R. vestiaria. RUDISTES. Lam. A family of the order Conchifera Monomyaria, Lam. the shells of which are described as irregular, very inequivalve, without distinct umbones; the ligament, hinge and animal entirely unknown. The shells contained in this family may be thus distinguished. 1. CALCEOLA. Large valve conical; attached by a flat space between the umbones, which form the extremities of the shell. Fig. 194. 2. HIPPURITES. Large valve cylindrical, with two internal lobes or varices. Fig. 198. 3. SPHÆRULITES. Large valve attached, including _Radiolites_. Birostrites is proved to be the cast of a Sphærulites. Fig. 193, 196. 4. HIPPONYX. Flat valve attached, upper valve conical. Fig. 199, 200. RUDISTES. Bl. The second order of the class Acephalophora, Bl. containing the genera Sphærulites, Crania, Hippurites, Radiolites, Birostrites and Calceola. RUDOLPHUS. Lam. MONOCEROS, Auct. RUFOUS. Reddish brown. RUGOSE. Rough, rugged. RUPELLARIA. Fl. de Belvue. An unfigured shell placed by De Blainville in a division of the genus Venerirupis. RUPICOLA. Fl. de Belvue. A shell described by De Blainville as an equivalve, terebrating species of ANATINA. A. rupicola, Lam. SABINEA. A genus of shells resembling small species of LITTORINA, as L. Ulvæ, &c. of our shores. SADDLE OYSTER. PLACUNA Sella, so called on account of a resemblance in shape to a saddle; the part near the umbones being flat, and the ventral margins being turned up in a sort of fluting or peak. SAGITTA. (_An arrow._) An ancient name for Belemnites. SALIENT. (_Saliens._) Jutting out, prominent. SALPACEA. Bl. The second family of the order Heterobranchiata, Bl. containing no genera of shells. SANDALINA. Schum. CREPIDULINA, Lam. A genus of microscopic Foraminifera.