Part 65

RICINULA. Lam. (Resembling the seed-vessel of the Ricinus.) Fam. Purpurifera, Lam. Entomostomata, Bl.--Descr. Sub-ovate, thick, tuberculated; spire short; aperture narrow, terminating anteriorly in a short canal; outer-lip thickened, denticulated within, digitated without; columellar lip spread over a portion of the body whorl, and granulated.--Obs. This interesting genus is composed of some neat little shells allied to Purpura, from which they are distinguished by the finger-like branching of the outer lip, and the granulations of the columella. Fig. 413, R. Horrida.

RIGHT. See DEXTRAL.

RIMULA. Defr. A genus consisting of a minute species of EMARGINULA, Auct. which has a fissure near the margin, but not reaching it. R. Blainvillii, fig. 243.

RIMULINA. D'Orbigny. A genus of microscopic Foraminifera.

RINGICULA. Deshayes. A genus founded on Auricula ringens of Lamarck and several small fossils, resembling in some respects Pedipes of Adanson; they would belong to Tornatella, were it not for the lips being thickened and marginated, fig. 540, A. ringens.

RISSOA. Freminville. Fam. Ellipsostomata, Bl. Melaniana, Lam.--Descr. Oblong, turrited, acuminated; spire long, consisting of numerous whorls; aperture round or oval, pointed posteriorly, dilated anteriorly; outer lip slightly thickened, emarginated, operculum horny.--Obs. The Rissoæ are small white, marine shells, considered by some authors as resembling Melaniæ, but placed by Sowerby near the Scalariæ. They are principally from the shores of the Mediterranean, and are also very abundant on the British shores, as well as the East and West Indian. Fig. 346, R. reticulata.

ROBULUS. Montf. A genus of microscopic Foraminifera.

ROLLUS. Montf. A genus composed of CONUS Geographus, Auct. fig. 462, and other species, rather cylindrical in form, and having a coronated spire.

ROSALINA. D'Orb. A genus of microscopic Foraminifera.

ROSTELLARIA. (From rostrum, a beak.) Fam. Alatæ, Lam. Siphonostomata, Bl.--Descr. Turrited, fusiform, thick, smooth or ribbed; aperture oval, terminating anteriorly in a long canal, posteriorly in a channel running up the spire; outer lip dilated, thickened, sometimes digitated, running up all or part of the spire, with a sinus near the anterior canal; inner lip smooth, spread over part of the body whorl and of the spire. The Red Sea and the Indian Ocean produce the few known species of this genus.--Obs. HIPPOCHRENES is the name given by De Montfort, to those fossil species which have the outer lip simple and very much dilated. R. curvirostrum, fig. 412. APORRHAIS is a name given to another proposed genus, composed of Rostellaria pes-pelecani, Auct. fig. 404. and similar species.

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.