Above, brownish black; upper wings varied with bluish grey scales, many near the outer margin arranged into a somewhat regular series; a transverse, slightly bent, white band runs from near the outer edge close to the tip, to near the middle of the wing; wings fringed with greyish and black; under wings brownish black, with fulvescent orange spots and a band, one small spot somewhat transverse, near the middle, beneath this a broadish band extends from the anal margin nearly to the outer side of wing, which is divided by a brown line, leaving an irregular squareish spot, attenuated towards the outer margin; on the margin are three differently-shaped dots beginning from the internal margin, and in one of the specimens are four slight lunules, growing fainter as they approach the outer margin. Beneath, upper wings with two transverse fulvescent orange bands, one near the centre, the other at the tip, broadest externally, with three black spots, the outer largest running into it near the margin, interiorly it is much contracted ending in spots; the base of the wings is yellowish grey, under wings yellowish grey at base, otherwise very similarly marked, the outer part of the orange band having two longitudinal whitish lines on it; antennae at base fringed with white; club brown. Body above silky yellowish brown; borders of segments lighter; beneath, greyish white. Inhabits King George's Sound. Capt George Grey. This seems to belong to a new genus not far removed from Castnia or Coronis. Hecatesia thyridion, Feisthamel. Illustration 25 Insects 8. 1. Hecatesia thyridion female. 1a. do. male upper side. 1b. under. 1c. fenestra in wing of male. 1d. section of fenestre. 2. Hecatesia fenestrata male. Lepidopt. Voyage Favorite Supplement plate 5 f. 1 male. Female alis longioribus, maculis albis triseriatis alarum anticarum majoribus, nulla macula diaphana fenestrata ad costam. The genus Hecatesia was founded by Boisduval in 1829,* upon a singular Zygenidous insect sent to Latreille by Mr. Alexander Macleay, from New Holland, in some part of which it does not seem to be uncommon. (*Footnote. Essai sur une Monographie des Zygenides page 11.) The species H. fenestrata Boisduval (l.c. page 11 plate 1 f. 2) was brought by Mr. Hunter, Surgeon of Captain King's expedition, and by him presented to the British Museum. Another species has been described by the Baron Feisthamel in the voyage of the Favorite (page 19 plate 5 f. 1) under the name of H. thyridion.* Of this species there are specimens in the collection presented to the British Museum, and I take the present opportunity of describing the female of this species, only remarking that it wants the fenestrated clear space in the upper wing.** (*Footnote. Lepidopteres nouveau, etc. Supplement a la Zoologie du voyage autour du monde de la Favorite sous le commandement de M. Laplace capitaine de Fregate.)