We have already intimated our belief that _Murex_ and _Cassis_ represent two equivalent groups; and these, as containing several established genera, we shall consider as sub-families: giving them the usual termination of _inæ_. Those higher naturalists, who have long since abandoned the belief in absolute divisions and isolated genera, are fully aware that no groups are more likely to exhibit the arrangement of nature, than such as contain numerous species, under a great diversity of forms. The _Murices_ are of this description, and appear to exhibit, among themselves, a circular series. _Triton_ and _Murex_ also seem typical genera, and of equal value. _Ranella_ obviously belongs to the first; yet, as it is merely a subordinate type of form, we cannot, under this belief, retain it as a _genus_, without a manifest inconsistency; unless, indeed, it is thought expedient to consider the types of form in _Murex_, as so many genera, and elevate three others in _Triton_ to the same rank; a refinement in nomenclature, which we cannot think is in the least degree necessary. * * * * * * [Illustration: EUTERPE _Terea_.] EUTERPE Terea. ---- PAPILIO. (_pars._) _Latrielle._ SUB-FAMILY PIERESINÆ. _Nob._ GENERIC CHARACTER. _Antennæ_ lengthened, terminating in a broad, very compressed, spatulate club. _Palpi_ hairy; the first joint very long, exceeding the united length of the two next: second joint half as long as the first; third very small, manifestly shorter than the second. _Anterior wings_ long, papilioniform; the exterior margin longer than the posterior. _Nob._ ---- SPECIFIC CHARACTER. _Wings above black: anterior both above and below, with a trifid white or yellowish central spot: posterior with a four-parted rosey spot; and varigated beneath, at the base, with yellow and rosy stripes._ Papilio Terias. _Latrielle & Godart. En. Meth. 1. p. 38. No. 39._ ---- Nature has so completely disguised this Butterfly in the form and colours of a genuine Papilio, as to have deceived the first entomologist now in Europe, and his most skilful and accurate coadjutator. In the _Ency. Methodique_ we find this species recorded as a _Papilio_; whereas it perfectly agrees, in all the details of its structure, with the characters proposed in that valuable work for the genus _Pieris_. Whether nature has employed this beautiful device to indicate the group which next succeeds in her series, or whether she has intended it to point out a strong analogy, are questions which, in our present imperfect knowledge of Lepidopterous groups, cannot be answered. Of this group we possess several new and highly interesting species. It is worthy of remark, that they were all collected in one particular locality, and at the same season. This was during a short residence at Mandioca, the plantation of Dr. Langsdorff, among the woods at the base of the Organ mountains, near Rio de Janeiro.