In every natural group of the diurnal Lepidoptera which we have analysed, (and the number is somewhat considerable,) there is always one in which the posterior wings are more than usually tailed; and this seems to be such a prevalent form throughout the Vertebrata and the Annulosa, that we believe it is universal: in other words, that it is one of the PRIMARY TYPES of Nature. We have consequently termed it the _natatorial_, since it represents that order of birds, as the Swallow-tailed _Papiliones_ typify the Swallows. That we should find this form in a group where the chief character is the roundness and the integrity of the wings, is certainly astonishing; but it shews that the laws of Nature are as simple, as they are universal. The absolute union of this sub-genus with _Lycæna_, with which we commenced the circle, is palpable to the meanest capacity. All the species we possess, are from Africa and India. As they represent the _Argynninæ_, we accordingly find them ornamented with silver spots. The species now figured, are probably male and female, and were received from Africa. We have now given the natural types of an Entomological genus; the only one that has been attempted, since the demonstration of _Phanæus_ and _Scarabæus_. These are but three genera, out of many thousands, which at present have any other foundation, strictly speaking, than mere opinion. But the great principles of variation are now discovered, and we must hope that those naturalists of a higher order, who join acknowledged talent to matured experience, will follow up the subject. * * * * * * GENERAL INDEX _OF THE PLATES TO_ VOL. III. IN THE ORDER OF PUBLICATION. ---- No. 21. pl. Trichoglossus Swainsoni 92 Protesilaus Leilus 93 Cressida Heliconides 94 Papilio Memnon 95 Caracolla acutissima 96 No. 22. Prinia familiaris 97 Amphrisius Nymphalides 98 Achatinella pica 99 ---- perversa 99 ---- acuta 99 Murex eurystomus 100 Polydorus Thoas 101 No. 23. Ptiliogonys cinereus 102 Plecocheilus undulatus 103 Protesilaus Swainsonius 104 Podalirius Pompilius 105 Leptocircus Curius 106 No. 24. Trogon Mexicanus 107 Achatinella bulimoides 108 ---- livida 108 Phyllonotus Imperialis. var. 109 Petreus Thetys 110 Zeonia Heliconides 111