Part 18

3. PRODUCTA. The same, valves produced, overwrapping; including Leptæna. Fig. 206, 206*.

4. TEREBRATULA. Hinge of the upper valve produced beyond that of the other, with a pit or foramen; including Delthyris, Orthis, Trigonosemus, Magas, Strophomena. Fig. 202, 205, 207, 208, 209.

5. SPIRIFER. The same, with deep triangular area; spiral folds in the interior; including Trigonotreta and Cyrtia. Fig. 204, 214, 215.

6. THECIDIUM. Large valve attached; curved ridges in the inner surface; two jutting points or teeth on the hinge. Fig. 216.

7. CRANIA. Attached by the surface of the valve; muscular impressions four, forming a face. Fig. 197, a, b.

8. PYCNODONTA. Irregular; hinge with raised pointed teeth. Fig. 217, 218.

9. PENTAMERUS. Valves divided by septa; including Gypidia. Fig. 210 to 213.

10. LINGULA. Valves equal, gaping, with a peduncle. Fig. 219.

BRACHITOMA. Swainson. A genus composed of PLEUROTOMA strombiformis and similar species, described as "sub-fusiform; resembling a small Strombus or Fusus; spire and aperture of equal length; canal short; outer lip slightly ascending, and forming a short canal; sinus very small and nearly semicircular; inner lip thickened above. B. Strombiformis, Sow. Man. fig. 381." Europe, East and West Indies, China, &c.

BRANCHIFERA. Bl. The second family of the order Cervicobranchiata, containing the following genera of symmetrical univalves:--Fissurella, Emarginula, and Parmophorus.

BRISMÆUS. Leach. Order. Pedunculated Cirripedes. Lam.--Descr. Seven plates, three pairs lateral, one dorsal; form cylindrically conical; pedicle not described. Hab. Holes in corals. B. Rhophodius, fig. 38.--Obs. This minute shell most nearly resembles Pollicipes Mitellus, fig. 37*, but the difference may be seen at once by comparing the figures.

BRONTES. Montf. This generic name is given to such species of MUREX as have a very long, closed canal; with a short spire, circular aperture, and are destitute of spires and ramifications. Brontes (Murex) Haustellum, fig. 390.

BUCARDIA. Schum. ISOCARDIA, Auct.

BUCCINUM. Linn. Fam. Purpurifera, Lam. Entomostomata, Bl.--Descr. Subovate or oblong, covered with an epidermis; spire turrited, consisting of few whorls; aperture wide, subovate, terminating anteriorly in a very short canal, reflected over the back; outer lip simple, slightly reflected; inner lip spread over a portion of the body whorl, terminating in a thick, smooth columella; operculum horny. Hab. British Seas, Northern Ocean, and Coast of Africa. Most of the fossil species occur in Crag, some in upper marine formation and London clay.--Obs. There are considerable difficulties in keeping this genus distinct from others nearly related to it, into which many of the species run by imperceptible gradations. The genus Nassa has been separated on account of the little notch, which terminates the columella. Some species of Terebra come so close upon the Buccina, that it is difficult to say where one genus ends and the other begins. T. Buccinoides, fig. 427. Buccinum Undatum, the common Whelk, fig. 421.

BUFO. Montf. A generic division of the species composing Ranella, characterized as having the shell not umbilicated. Ex. R. ranina, fig. 394. The above character is scarcely sufficient in some cases, even as a specific distinction.

BULBUS. Humph. RAPELLA, Swainson. A genus formed for the reception of PYRULA papyracea, Auct. (fig. 389), and similar species. RAPANUS, Montf.

BULIMIMA. Montf. A genus of microscopic Foraminifera.

BULIMULUS. Leach. Fam. Colimacea, Lam. The author is unacquainted with the characters by which the two or three species included in this genus are to be distinguished from Bulinus. We have represented, fig. 283, Bulimulus trifasciatus, Leach, (Bulinus Guadaloupensis, Auct.) This occurs in the same limestone which encloses the half fossilized human remains from the Grand Terre of Guadaloup. Several species are described by the Rev. L. Guilding in the Zoological Journal, namely, the B. Undulatus, Antiguensis, and Proteus; but neither from the shells themselves, nor from the figures of the animal, can we draw any information as to the generic character; the difference alleged by Mr. Swainson and Mr. Gray being a comparative thinness in the outer lip.

BULINUS. Brug. (Bulinus, Lam.) Fam. Colimacea, Lam. Limacinea, Bl.--Descr. Oval or oblong, light, covered with a thin epidermis; spire obtuse, variable in length and in the number of whorls, which are generally few; aperture wide, oval, rounded anteriorly; outer lip simple, usually reflected, joining the columella without a sinus; inner lip reflected over part of the body-whorl. The Bulini are land shells, found in many parts of the world.--Obs. The genus Bulinus can only be distinguished from Helix by its oval form; it forms part of the genus Helix of De Ferrusac, under the sub-generic designation of Cochlostyla. It is known from Achatina by the absence of the notch at the point of union between the inner and the outer lips. The young are produced from eggs, which are as firm and opaque as those of birds. (See Introduction.) Bulinus rosaceus, fig. 282. B. Guadaloupensis, fig. 283. B. Lionetianus, fig. 284. B. lubricus, fig. 285. Many new species were brought to this country by Mr. Cuming, and are represented in the Conchological Illustrations, published by the Author at 50, Great Russell Street, Bloomsbury, (in parts 21, 22, 23, 26, 27, 30, 31, 34, 35, 137 to 146, 185, 186.) Species occur in Europe, West Indies, Brazil, and South America generally. Some small species are British.

BULLA. Auct. Fam. "Bulléens," Lam. Akera, Bl.--Descr. Generally thin, smooth, oval, oblong or cylindrical, more or less convolute; spire short, depressed, or hidden by the last whorl; aperture long, wide in front, gradually narrowing towards the spire; outer lip thin; inner lip spread over a part of the last whorl.--Obs. The shells composing this genus are very variable in form. The light horny species with an elastic lip is called Akera, fig. 247. The more decidedly convolute species with hidden spires are the Atys, Montf. B. Naucum, fig. 250. B. Lignaria, fig. 251, is Scaphander of Leach. The light, thin species, with extremely wide aperture, fig. 248, is Bullæa aperta, Lam. The genus Bullinula of Dr. Beck, consists of those species which have more produced spines, fig. 253. The Bullæ are marine, and inhabit all climates. The fossil species occur in tertiary beds.

BULLÆA. Lam. BULLA aperta, Auct. fig. 248.

BULLÆANA. ("Bulléens, Lam.") A family belonging to the first section of Lamarck's order, Gasteropoda, containing the genus Bulla. The genera Bullæa, Akera, Aplustra, Atys, Scaphander, Bullinula, into which it has been divided, may all be fairly included under the name BULLA.

BULLIA. Gray. A genus of shells partly resembling Buccinum, and Terebra in general form, being more elongated than the former and more ventricose than the latter. Mr. Gray remarks in the Synopsis of the British Museum, page 114, that the Bulliæ resemble the Nassæ in most characters, "but they have a very large, broad foot, and the hinder part of the inner lip of the shell being extended beyond the mouth, forms a raised enamelled band round the suture of the whorls, as is also the case with the Ancillariæ and some Volutes." Bullia vittata, fig. 427, is an example of the genus. The name Subula is given by De Blainville to the other species of Terebra, so that if both these genera were admitted, the old genus Terebra must be expunged.

BULLINULA. Beck. Species of BULLA, with produced conical spires, fig. 253.

BYSSOARCA. Sw. (Byssus and Arca.) Fam. Arcacea, Lam. A genus of bivalve shells, composed of the Arca Noæ, and several other species, separated from the genus Arca on account of their shells being attached by means of a byssus passing through an hiatus in the ventral margins. B. Noæ, fig. 132. The species occur in Southern Europe, East and West Indies, China; also, on the coasts of Great Britain.

BYSSOMYA. Cuvier. (Byssus and Mya.) De Blainville states that although the shell of this proposed genus resembles Saxicava, the animal is sufficiently different to justify the separation.

BYSSUS. ([Greek: Bussos], byssus, ancient name for linen.) The tendinous fibres by which some Bivalves are as it were anchored or moored to sub-marine substances. A fine example of this is to be seen in the Pinnæ which bear some resemblance to large Muscle Shells and have an hiatus in the margins of the valves through which a bunch of silken fibres passes. In the British Museum there is preserved a pair of gloves which have been woven of these fibres. The Byssus is peculiar to some bivalve shells such as Muscles, Hammer Oysters, Arca Noæ, &c.

CALCAR. Montf. (a spur.) A genus composed of TROCHUS STELLARIS, Lam. and other depressed species of Trochus which are characterized by a stellated keel round the angle of the last whorl; but not including T. Imperialis, which is the genus Imperator, Montf. The difference consists in the latter being umbilicated and the former not. T. stellaris, fig. 358.