&metes& Cuvier observes that this form approaches very closely to that of his Bundle, but he adds that be does not find sufficient certainty in the imperfect materials afforded by Adanson to enable him to found either a genus or even a species on them. De Blainville places it as a genus next to Ixobaria ; but his description add figure are taken from Adanson, tutd•he is obliged to add that it is established upon an animal " &Baez incornpletement connn." Bella. Besides the true Bull ids, the heterogeneous Bulla of Linnmus comprised some of the Physa and Achatinw, and of the Ovule, Terebella, Pyrulee, ke.: in short, the genus comprised animals of entirely different organisation. Terrestrial and marine testacea—tho former breathing air and the latter respiring water-a-were there placed side by side. Lamarck retains the name (and Curler scents to adopt his arrangement) for the species whose shell covered by a slight epidermis is sufficiently large to afford a retreat to the animal, and is more perfectly rolled up than the shell of Bullwa. Lamarck describes the shell of his Bella as completely rolled up (enroulde), showing itself constantly uncovered. It is, generally speaking, only partially enveloped by the animal, which can retreat into it almost entirely; has no distinct colutnella nor any true spire, unless indeed that term be applicable to the apex of Bella fragilis, which we now proceed to describe. Its shell is ovnte-oblong,.very thin and fragile, of a horn colour, with very small transverse strite, and the apex rises into the rudiment of a projecting spire.
It is the Akera bullata of 0. F. Muller, and is not uncommon on the British coasts. We now proceed to give an example of those species which, while they have a little more solidity than Bulla fragilis, are still very delicate and fragile in their texture.
B. Velum. The shell is very delicate, of a very light horn-colour when in fine condition, with a anow.whito band about the middle, bordered on each side with a broad dark-brown one ; the apex and base are white, both bordered with dark brown bands.
B. ampulla. The shell is ovate and subglobose, beautifully mottled with white, plum-colour, and reddish. Instead of a spire there is an umbilical alveolus. Lamarck gives as a locality both the Indian and American oceans; Deshnyes, the European ocean and the Indies.
B. lignaria (Scaphandci Ugnarius) is a common species on our coasts. It has a testaceous stomach or gizzard, so well known as the vehicle of Giani's half error, half fraud. He found these test aceou.a gizzards and elevated them immediately to the rank of shells sui generis' literally, for he gave the genus his own mune, and imposed upon many : he went so far as to describe the habits of his pretended testaceous animal. Draparnaud first exposed this piece of
charlatanerie.
B. Hydates, Linn:cue, and B. Cranchii, Leach, are found in the British seas. B. Media, Philippi, l3. columna, Chiaje, are recorded as British, but may be regarded as doubtful.
The following genera of Bullida, are found in Great Britain :— Cyliehne, eight species [Cvmensa]; hyalina ; Tornatella fasciata Akera bullata: Bella, two species ; Scaphander lignarius ; Philine, six species.
Fossil Bullichr.
Lamarck enumerates four fossil species, all of them from Chignon ; G. Sowerby says that such are only to be distinguished in the Tertiary Beds and in the Greensaud. Deahayea in his tables, speaking of tertiary fossils only, gives two fossil species of Bullwa, one from the sub-Apennine Beds, and one from Paris. Of Biala he enumerates twenty-three fossil in the Tertiary Beds; and of these, two are both living and fossil, namely, B. lignaria and B. ampulla. The first he places in Sicily, in the sub-Apennine Beds (Italy), and the English Crag at Bordeaux and Dax, in Touraine, at Turin, Angers, Paris, and Valognes; in short, in the beds of the Pliocene, Miocene, and Eocene periods of Lyell. The second, Deslinyea quotes as occurring in beds of the Pliocene period only, namely, those of Sicily and the sub Apennine Beds (Italy). In his edition of Lamarck (vol. vii., I836,) he takes no notice of B. ampulla as a fossil, but notices B. striata (which he observes has been confounded with B. ampulla) as a fossil species. Ho also remarks on the confusion between B. aolida and 11. cylindrica, and proposes that B. solider should take the name of B. cylindrica; that the B. cylindrica of Bruguieres, living in the Mediterranean and European seas, should be called B. cylindracea (Pennant's name); and that the fossil Balla from the environs of Paris, confounded with the latter, should be named B. Bruguihei.
De Blainville places under his family of Act-rata, the genus Gasteroptera, whose body is divided into two parts, the posterior being globular and joined by a peduncle to the anterior portion, which is small, but enlarged on each side into a con siderable muscular expansion - trans versely oval, and cut or hollowed out in the middle, both above and below, rendering the expansion bilobated, as it were, and an organ for swimming, in place of a foot for creeping. The lateral gill is uncovered; there is no shell. Example, G. Meekeli, from the Sicilian seas.