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Show 348 MOLLUSCA. AKERA, Muller. The branchire covered, as in the preceding genera, but their tentacula are so shortened, widened and separated, that they seem to be totally wanting, or rather to form a large, fleshy, and nearly rectangular shield, under which are the eyes. Independently of this, the herma. phroditism of these animals, the position of their genital organs, the complication and armature of their stomach, and the purple liquid effused by several of their species, approximate them to the Aplysire. The shell, of such as have any, is more or less convoluted, but with little obliquity, and is without a projecting spire, emargination, or canal; the columella, projecting convexly, gives a crescent-like figure to the aperture, the part opposite to the spire being always the broadest and most rounded. M. de Lamarck names those in which the shell is concealed in the thickness of the mantle, BuLLlEA· It has but very few whorls, and the animal is much too large to be drawn into it. Bullrea aperta, Lam.; Bulla aperta and Lobaria quadriloba, Gm.; Phyline quadripartita, Ascan.; Mull., Zool. Dan., III, pl. ci; Blanc., Conch. Min. Not., pl. xi; Cuv., Ann. du Mus. t. I, pl. xii, 6(1). The animal is whitish, and about an inch long; the fleshy shield, formed by the vestiges of its tentacula, the lateral swellings of its foot, and the mantle occupied by the shell, seem to divide its upper surface into four lobes. Its thin, white, semi-diaphanous shell, i5 nearly all aperture, and its giz· zard is armed with three very thick rhomboidal pieces of bone. It is found in almost every sea, where it lives on oozy bottoms. M. de Lamarck leaves the name of BuLLA(2) to those species whose shell, merely covered with a slight epidermis, is large enough to shelter the animal. It is somewhat more convoluted than in Bullrea. Bulla lignaria, L.; Martini, I, xxi, 194, 95; Cuv., Ann. du Mus., XVI, 1; Pol. Test. Neap., III, pl. xlvi. The oblong shell, (1) The Sormet, Adans., Senegal, pl. i, f. 1, is a species closely allied to Bul· l;ea; but I cannot establish a genus, or even a species, upon so imperfect a docu· ment. (2) The genus Bulla, Lin., not only comprised the .O.lcerre, but also the Juri· ~Ire, .O.gatintB, Physre, Ovulre and Terebella, animals between which there is much difference. Brugieres commenced the work of reformation by separating the .llgatinEB and the .B.uriculre, which he united to the Lymnei in the genus Bulimru; M. de Lamarck finished it by .creating all the genera we have just named. GASTEROPODA TECTIBRANCHIAT A. 349 with its concealed spire and ample aperture, very wide anteriorly, resembles a loosely rolled lamina, streaked in the direction of its whorls. The stomach of the animal is armed with two large semi-oval osseous pieces, and with a small compressed one( 1 ). Bulla ampulla, L.; Martini, I, xx~i, 20, 204; Cuv., Ann. du Mus., XVI, 1. The shell oval, thick, clouded with grey and brown; the stomach furnished with three black, very convex rhomboidal pieces. ' Bulla ftydatis, L.; Chemn. IX, cxviii, 10 19; Cuv., Ann. du Mus., XVI, 1. Shell round, thin, and semi-diaphanous; the last whorl, and conseq.uently the aperture, higher than the spire; three small scutelhform pieces in the gizzat·d(2). We reserve the na~e of AKERA, properly so called, DonmwM, Meek., LoBARIA, Blamv., for those species which have no shell whatever, or only a vestige of one behind, although their mantle has its external form. A small species, Bulla carnosa, Cuv., Ann. du Mus., XVI, 1; Meek., Anat. Compar., II, vii, 1, 3; Blainv. Malac., pl. xlv, f. 3, is found in the Mediterranean. The only armature of the stomach is the mantle; its fleshy resophagus is extremely thick. A tuberculous species, Doridium Meckelii, Delle Chiaie Memar., pl. x, f. 1-5, inhabits the same sea. The GASTROPTERoN, Meek. Appears to be an Akera, the margin of whose foot is extended into broad wings, used in natation, which it effects on its back. It has no shell, nor has the stomach any armature; a slight fold of skin is the only vestige of a branchial operculum that is perceptible. G. Meckelii; Rosse, Diss. de Pteropoclum Ordine, Haire, 1813, f. 11-13; and Blainv., Malacol., pl. xlv, f. 5; or Clio amati Delle Chiaie, Memor., pl. ii, f. 1-8. A small animal an inch long and two broad, the wings being extended. From the Me-diterranean. . (1 l Gioeni having observed this stomach separate from the animal, mistook it for a sh:ll, and made a genus of it, to which he gave his own name (The Tricla ~f ~etztUs, Char, Brug.). Gioeni even went so far as to describe its pretended ab•ts. Draparnaud was the first who perceived this mixture of error and fraud. (2) Add, Bulla naucum;-Bulla physis. Muller describes smaller ones, such as the .fl.kera bullata, Zool. Dan., LXXI, or Bulla akera, Gm. |
