Family two, the Gastrochænidæ, is a somewhat heterogeneous one, as it contains Saxicava and Aspergillum. We have only space for a short account of the latter, the animal which has received the strange name of the Watering Pot, and is represented in Fig. 135. It inhabits a calcareous tube, thick, solid, of considerable length, and nearly cylindrical, presenting at one extremity an opening fringed with one or many foliaceous folds in the form of frills, and at the other extremity a convex disk, pierced with holes like a watering-pot: whence its name. The animal is attached by certain muscles to the interior of the tube. Chenu, to whom we are indebted for our information respecting this curious mollusc, tells us "that the animal which inhabits this curious shell was first described by Russell, whose account of it is deficient in the anatomical details, which might explain the utility of the holes in the disk of the central fissure, and of the spiriform tubes found there." We suppose that this arrangement is necessary in order to facilitate respiration; and M. De Blainville thinks the small tubes are intended for the passage of the fillets which are necessary to fix the animal to the body on which it is to live, and in such a manner as to admit of its movements round a fixed point. [Illustration: Plate XX.--Temple of Serapis at Pozzuolo.] [Illustration: Fig. 135. Aspergillum vaginiferum (Lamarck).] The animal which inhabits the _Aspergillum_ is elongated, contractile, and only occupies the upper part of the tube, but it can stretch itself out sufficiently for all its wants. Shells of this genus are very rare, although a great number of species are known. They are found in the Red Sea, and in the seas of Australia and Java. The shells are generally of a white or yellowish tint; some have the tube covered with a glutinated sand, mixed with small fragments of shells of diverse colours. We know nothing of their habits, and their singular forms have left naturalists in doubt as to the place which should be assigned to them in the method of arrangement. It is only after having recognized the existence of two valves, which was detected with great difficulty just under the disk, and forming part of the sheath in which the animal is encased, that it has been decided to range them with the _Tubicola_, and with the shells presenting an arrangement analogous or equally singular. These molluscs are, as M. Chenu says, little known, rare, and hence much sought for by collectors. They are exclusively exotic, the most common species being from Java. It is imported into Europe by the Dutch. Our third family, the Anatinidæ, includes Myochama, Pandora, Lyonsia, Myacites, Pholadomya, Thracia, and Anatina, genera which were more important in the former than in the present seas; some, in fact, being wholly extinct, or represented, as in Pholadomya, by one or two living species. Our fourth family, the Myacidæ, including Gycimeris, is found only in