Part 78

VEXILLA. Sw. A genus of "Nassinæ," Sw. thus described: "General shape of Purpura, the inner lip flattened and depressed; the outer, when adult, thickened, inflected and toothed; aperture wide; picta Sw. Chem. pl. 157, f. 1504-5." Sw. Malac. p. 300.

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

VITRELLA. Sw. A sub-genus of "Bullinæ," Sw. Lardn. Cyclop. Malac. p. 360.

VITRINA. Drap. (Vitreus, glassy.) Fam. Limacinea, Lam. and Bl.--Descr. Ovate, thin, glassy, fragile; spire short; last whorl large; aperture wide, transverse; peritreme simple; columella spiral, linear.--Obs. This genus of land-shells is not known in a fossil state. The recent species are found among moss and grass, in shady situations. De Ferussac has divided this genus into Helicolimax, fig. 263, and Helixarion, fig. 262.

VITULARIA. Sw. A genus of "Muricinæ," Sw. thus described: "General habit of Muricidea, but the inner lip is depressed and flattened as in the Purpurinæ; varices simple, nearly obsolete. Tuberculata, Sw. En. M. 419. fig. 1. (Murex vitulinus, Auct.)" Sw. p. 297.

VIVIPARA. A generic name given by Montfort, and retained by some authors for PALUDINA, Lam. on account of the animals being viviparous, i. e. the young being perfectly formed before they leave the ovaries.

VIVIPAROUS. See VIVIPARA.

VOLUTA. Auct. (Volvo, to revolve.) Fam. Columellaria, Lam. Angyostomata, Bl.--Descr. Sub-ovate, rather angulated, thick, generally tuberculated, smooth; spire short, conical, with a mammillated apex; aperture generally angulated, large, terminating anteriorly in a deep notch; columella smooth, with several plaits, of which the lowest is the largest; outer lip thickened within.--Obs. The genus Voluta, as left by Linnæus, is only characterized by the folds on the columella, and includes many shells which, although they agree in this respect with the genus, are yet quite opposite to each other in all other characters. Thus the Auriculæ, which are land shells, and have the aperture entire, are mixed up with others which are marine, and have a canal, as Turbinellæ, and the Fasciolariæ, and others which have merely a notch, as the true Volutes. This genus, as it is circumscribed at present, includes a great number of beautiful shells, most of which are rich in colouring. CYMBA and MELO have been separated by Mr. Broderip from the genus VOLUTA of Lamarck, for reasons stated in their respective descriptions. Fig. 443.

VOLVARIA. Lam. (Volva, a shuttle.) Fam. Columellaria, Lam.--Descr. Cylindrical, convolute, spirally striated; spire very short, nearly hidden; aperture narrow, as long as the whole shell; columella with three oblique plaits; outer lip dentated.--Obs. The Volvaria are only known in a fossil state, and resemble some species of Bulla in general form, but are distinguished by the plaits on the columella. Fig. 439, V. concinna.

VOLUTELLA. Sw. (A little volute.) A genus composed of those species of MARGINELLA, Auct. which have the spire concealed, and the aperture smooth within. Fig. 438, PERSICULA of Schumacher.

VOLUTILITHES. Sw. (Voluta, and [Greek: lithos], lithos, a stone.) A genus composed of some fossil species of Voluta, which have the plaits on the pillar generally numerous, indistinct, and sometimes wanting altogether, with a pointed spire. Fig. 436, V. spinosa.

VOLUTION. See WHORL.

VORTICIALIS. Lam. A genus of microscopic Foraminifera.

VULSELLA. Lam. (A little tongue.) Fam. Ostracea, Lau. Margaritacea, Bl.--Descr. Equivalve, irregular, longitudinal, compressed, oblong; umbones separated by a slight area in both valves; hinge with a large pit in the centre, containing the cartilage, the ligament being spread over the areas; muscular impressions, one on each valve, sub-central, oblong.--Obs. This genus differs from Ostræa in the equality of the valves, and in having a hollow pit in the hinge for the cartilage. Vulsella lingulata, fig. 185.

WATERING-POT. Aspergillum, fig. 44, commonly so called on account of the resemblance of its perforated termination to that of the spout of a watering-pot.

WENTLE TRAP. Scalaria pretiosa, commonly so called.

WHORL. A complete turn or revolution round the imaginary axis of a spiral shell. The last whorl is called the body-whorl. The whorls are described as non-contiguous, when they do not touch each other; continuous, in the opposite case. Depressed when they are flat. They are angulated, heeled, or coronated; distinct, or indistinct. They are sometimes, as in Cypræa, hidden by the last whorl.

XYLOPHAGA. Sow. ([Greek: xulon], zylon, wood; [Greek: phagô], phago, to eat.) Fam. Tubiscolæ, Lam.--Descr. Equivalve, globose, closed at the back; with a large, angular hiatus in front; hinge with a small curved tooth advancing from beneath the umbones in each valve.--Obs. This shell, which is found in a cylindrical cavity, eaten in wood by the animal, resembles Teredo, but has not the shelly tube, nor the posterior hiatus. X. dorsalis, fig. 50, 51.

XYLOTRYA. Leach. XYLOPHAGA, Sow.

ZONITES. Montf. A genus formed of Helix Algira, and other similar species with depressed spires and large umbilici; included in the sub-genus Helicella. Fig. 279.

ZUA. Leach. A genus described as differing from Bulinus in having a polished epidermis, and a thickened, not reflected lip. Zua lubrica, B. lubricus, Auct.

ZURAMA. Leach. A sub-genus of Helix. H. pulchella, Auct. Gray's Turton, p. 41.

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EXPLANATION OF PLATES,

AND SYSTEMATIC VIEW OF THE

LAMARCKIAN ARRANGEMENT.

Class, ANNELIDES. Order, SEDENTARIA. Fam. Dorsalia.

FIG.