GENERIC CHARACTER.
Shell subquivalve, rough, deformed, generally lengthened and lobed or hammer-shaped: beaks small and divergent. Hinge without teeth, a lengthened conic hollow situated under the beaks and traversing obliquely the facet of the ligament. A lateral slope or groove at the side of the ligament for the passage of the byssus or beard with which the animal is furnished.
SPECIFIC CHARACTER.
Shell curved, with a single somewhat straight abbreviated lobe at the base: reddish yellow, clouded, spotted and dotted with fuscous.
Malleus Maculatus: testa arcuata, lobo basis unico sub-recta abbreviato flavo-rufescente fusco nebulosa maculata punctisque.
The singular object now before us, a shell no less remarkable for the peculiarity of its form than rarity of occurrence, is one of the most choice productions of the seas surrounding the Friendly Isles. The discovery of this shell, like that of many others, resulted from the assiduities of that eminent Naturalist and promoter of scientific knowledge, the late Sir Joseph Banks, and of Dr. Solander, who accompanied him in that memorable voyage of Captain Cook to the Southern Hemisphere, in which the Friendly Isles were discovered. The fine example of this shell, in particular, from which the drawing in our plate is taken, it may be also added, was one of those which were brought to this country by Captain Cook upon the return of the expedition, and which being shortly after presented to Sir Ashton Lever, remained in the Museum of that distinguished amateur from that period to the time of its dissolution in the year 1806.
When we consider the very remote situation of those islands, so distant from the usual track of all navigators, we cannot be surprised, admitting the species to be local in those seas, to find it has remained a very rare shell from the period of its discovery to the present time. In the course of many years only a few specimens have occurred to our observation, and while it has remained scarce with us, it appears to have been still more uncommon in the continental cabinets: very few of which, if we are informed correctly, were lately in possession of it.
The first difficulty that arises in the mind of the naturalist upon the inspection of this shell results from the ambiguity of its generical peculiarities: we pause to consider where it should be placed. Linnæus, to whom, as it will be observed, the present shell was totally unknown, arranged the Hammer Shell, its nearest approximation, among the Ostreæ. The Hammer Shell, or as it is more usually denominated the Hammer Oyster Shell, had been discovered before the time of Linnæus; it had appeared in the work of Rumpfius, Seba, Gualtieri and Argenville, and the shell had been examined and described by him in the Museum of Ulrica, Queen of Sweden, under the name of Ostrea Malleus. That the hinge accords in some degree with that of the Ostreæ generally must be admitted, at the same time that it possesses other characters less easily reconciled to that genus, unless we embrace the Linnæan genus in all its latitude, and to this the conchologist of the present day cannot accede, at least without some little difficulties.
The conformation of this shell is very striking, and yet we perceive that its essential characteristics are less definitive than could be wished; there are several approximations in the general figure to be found among shells which nevertheless possess characters generically distinct. For many years this shell was known in this country under the name of “Margaritifera maculata,” and the trivial English appellation of the “Spotted Hound’s Tongue:” it appeared under those names in the Conchological Museum of M. de Calonne, while it remained in England, and in the catalogue of that museum, which is still extant, it will be found under those names. The epithet of Hound’s Tongue is not inaptly applied to this shell, in allusion to the elongated form. The term Margaritifera does not refer to the form, but to the pearly gloss that appears upon the surface of the dark blue space lying within the shell, immediately below the hinge, and extending from thence about one fourth part of its whole length. This is the region in which the animal is attached by its ligament to the valves of the shell; besides which, a gloss of pearly hue is observed to pervade the whole of the inner surface, only that it is most conspicuous in the darker disk of the shell. As a secondary character this pearliness is very remarkable in the shell before us, at the same time that as a generical denomination the term Margaritifera assigned to it from this circumstance alone is liable to objection; because, the same pearliness prevails in many shells which have no relation whatever with the present, either in the form or structure of the hinge, and it is to these we must resort for its true essential character.