I think this may be the Scarites cyaneus Fabricius described from the Banksian Cabinet in 1775 (Systema Entomologiae page 249 g. 68 sp. 2.) It differs however from his description in the appendiculated thorax (the sides of which are rounded) being abruptly cut off behind, and in having the somewhat dilated margin there, slightly emarginate.  The general surface of the thorax is not so bright in colour as the elytra, it has more of a purple reflection; a dark greenish hue prevails over the elytra, the anterior edge of each having, towards the margin, a slight bend upwards, which forms a kind of tooth, projecting slightly over the somewhat dilated margin of the elytra, along the margin of these are at least eight points, at first seemingly impressed, but when more particularly examined they appear to be raised and to have an impressed line round each of them.  The head is black, the antennae and palpi piceous, the third joint in the former is longer than the second or third, the terminal joints are (more especially) furnished with pitchy hairs.  Long. lin. 8.

Habitat King George’s Sound.  Captain George Grey.

The genus Carenum was founded by Fr. A. Bonelli in the second part of his
Observations Entomologiques, read the 3rd May 1813 and published in the
Turin Transactions for 1813,* upon a specimen contained in the Paris
Museum of Natural History, which he regarded as the Scarites cyaneus of
Fabricius figured by Olivier.

(Footnote.  Memoires de l’Academie Imp. des Sciences etc. page 479.)

Guerin* has shown that the Arnidius marginatus Leach of the letter-press to the Voyage de l’Astrolabe, page 33, is synonymous with Carenum cyaneum of Bonelli, as he has seen the two specimens, the former of which is in Dupont’s collection.

(Footnote.  Crust.  Arachn. et Ins. of the voyage of the Coquille avant-propos page 7.)

M. Brulle* observes well that the Carenum cyaneum of Bonelli must be different from the Scarites cyaneus of Fabricius, as both these authors speak of its being blue (or deep blackish green) over the whole upper surface, while in the C. cyaneum the blue is confined to the margin of the elytra; besides Olivier expressly states that the Scarites cyaneus is smaller than the Scarites subterraneus, which will not at all suit the original specimen from which the learned Bonelli derived his generic character.  In the British Museum is the original specimen of Arnidius marginatus (catalogued by Dr. Leach) presented by J. Huey, Esquire, and it is very different both in size and in colour from the descriptions of Fabricius and Olivier, and the figure of the latter,** all derived from the original specimen formerly contained in the Banksian collection.  Dr. Boisduval’s concise description (op. cit. page 2, page 23) answers the specimen so named by Leach.

(Footnote.  Histoire Naturelle des Ins. par Messieurs Audouin and Brulle 5 page 64.)