[Footnote 2: Mr. Parkinson states, that in a trilobite which he possessed he thought he perceived the _points_ of the feet; but on endeavouring to detach the piece of rock in which it was embedded, the specimen was entirely shivered, though he worked at it with the utmost care. A portion of the underside of a trilobite (_Isotelus gigas_) near the anterior edge of the head, was distinctly ascertained, by Dr. Dekay, but only enough to convince him of its analogy in this part with that of the limulus polyphemus no organs of locomotion could be seen. Mr. Stokes, the distinguished fossilist of London, has confirmed the observation of Dr. Dekay, by some dissections of his own.] That these petrifactions were once marine animals there can be little doubt, for they are always found associated in the same rocks with shells, and other productions peculiar to the sea. The Trilobite is supposed by many naturalists to be one of the first animated beings of our earth called into existence by the great Author of nature.[3] It was first noticed more than two centuries ago, among the petrifactions which abound in a calcareous rock, at Dudley, in England, and was from this circumstance, called for a long time, the _Dudley fossil_. Linné gave it the name of the _Paradoxical insect_; but whether an insect, a crustaceous animal, or a shell, is still considered by many as problematical. [Footnote 3: It is obvious, that if most of the gelatinous animals which now inhabit our seas, were to become extinct, few or no traces of them could be found in any succeeding depositions of earthy matter. Whatever kind of animal life, therefore, may have been the first which appeared in our planet, must be entirely hypothetical. All that we can with certainty say of it, is, that it was best adapted to the circumstances, in which it was to exist, and that it was consistent with the wisdom and design which we see every where pervading the universe.]