We view this elegant, though common shell, as the type of the Lamarkean Mitres, a group we shall hereafter consider as a sub-family. It is common in various parts of the Asiatic Ocean, and sometimes occurs of gigantic size: in its natural state it is covered with a thin olive epidermis.
We regret that the nature of this work will not permit us to do more than furnish the clue, to the natural arrangement of the two typical groups of this family, Voluta and Mitra. The first of these we have, indeed, pledged ourselves to enter upon more fully in Exotic Conchology. But the arrangement of the Volutes is so intimately connected with that of the Mitres, that we scarcely know how to illustrate one, without perpetually adverting to the other.
The two typical groups of the Lamarkian Mitræ we now characterise from their shells; they correspond to those of the typical Volutes; while their internal relations may be learned from the respective types of form here designated. The genera Mitra and Tiara, each present a circular series of affinities, and are united by the fourth type in each group. Even a partial study of this disposition will reveal to the Conchologist a harmony of design, amid the greatest diversity of structure, which he could scarcely have suspected in the mere covering of an animal.
The shells which appear associated with M. episcopalis, in this type of form, are never coronated: the only external sculpture which they in general possess, are delicate rows of minute punctured dots, in the typical examples, as Pertusa, millipora, versicolor, the outer lip is acutely toothed; while in the aberrant species, Melaniana, tessellata, scutulata, &c. this part is smooth.
Pl. 50.
MITRANÆ Pl. 5.
1. Tiara isabella. 2. sulcata.
TIARA isabella.