These are remarkable looking beetles, easily distinguished by their broad flattened toothed antennae curving round on either side. The head is short and angular on the sides; the thorax flattened; and the elongate elytra truncate at the apex and not quite covering the tip of the abdomen. Most of the species are of moderate size, and reddish brown in colour; they are confined chiefly to Africa, the East Indies, and Australia. Most of the African species are said to dwell in ants’ nests, but though I have had several records of species being found under stones in ants’ nests, most of ours are found under logs, bark, or crawling about on the grass or ground. This family attracted the notice of entomologists at a very early date; Latreille formed the family to contain the two genera _Paussus_ and _Cerapterus_, which he called _Paussili_, afterwards changed by Leach to _Paussides_. Donovan described the first species from this country in 1815. Westwood has written a great deal about them; he monographed the family (Proc. Linn. Soc. 1849–1850); in his “Arcana Entomologica” he described a great many from Australia and other countries; others in the “Annals of Natural History,” 1851; and again figured others in his “Theosaurus Entomologica,” Oxen. 1874. Macleay added 32 new species (Trans. Ent. Soc. N.S.W. 1873), all belonging to the Genus _Arthropterus_; while Blackburn placed 3 more to the list 1891–1892, one of them in the typical Genus _Paussus_. _Arthropterus brevis_ is one of our smallest species; it measures slightly over ¼ of an inch in length; the antennae are rather short and broad; the thorax broad and rounded on the sides; the elytra expanded slightly to the truncate tips, leaving the apical portion of the abdomen exposed. This is our commonest species, and can be sometimes obtained in numbers near Sydney under the papery bark of the ti-trees. _A. humeralis_ comes from the Wellington district, and measures under ¾ of an inch; the antennae are large; the head angular; the body long, narrow, and rounded to the extremity, with the elytra short and truncate above the tip of the abdomen. General colour dark reddish brown, lightly clothed with short scattered brown hairs. Family 9. Ant Beetles. SCYDMAENIDAE. The members of this family are minute creatures of which little is known. Sharp says: “Allied to the _Silphidae_, with the hind coxae separated, and the facets of the eyes coarser; tarsi five jointed; the number of abdominal segments visible six.” It is owing to the Rev. R. L. King that we first knew anything about this group in Australia; he described about 15 species (Trans. Ent. Soc. N.S.W. 1864); to which 2 more have been added by Macleay and Sharp.