My reasons for establishing the family Thynnidae I shall expose in my monograph of that family, which would have been published ere this but for the difficulty of procuring specimens for dissection; and as I must for a similar reason defer the positive character until I publish the synopsis of the whole, I will give those negative ones which are comprised in the differences which distinguish it from Scotaena of Klug, and from which it may be separated by its much swollen and protuberant clypeus, being considerably less emarginate. Genae scarcely conspicuous. Antennae longer and more porrect; second submarginal cell as long as the third; abdomen broader at the base, its ventral surface concave; hypopygium scarcely carinated laterally, and pygidium prominent and deeply emarginate, its lateral edges produced into acute teeth. External differences apparently so small, and which might elsewhere be deemed inadequate to the establishment of genera, become important in this remarkable family, from their being confirmed by the structure of the trophi, and the strong distinctions exhibited in their females in every instance that has yet presented itself to me, wherever I have had the certainty of specific identity in these heterogynous insects, from the direct observation of my friends in Australia. Oncorhinus xanthospilos, Shuckard. Black--clypeus, mandibles, lower portion of face in front of eyes, a narrow streak above and behind them--anterior margin of collar, tegulae, tubercles and adjacent part of epimerae--a round spot on each side of each segment of the abdomen, except the terminal one--apex of the femora, the tibiae and tarsi, all yellow; the posterior tibiae being only brown within, and the extreme apex of the joints of their tarsi also brown. Habitat King George's Sound. Length 11 lines, expansion of the wing 18 lines. This is a unique species in the genus as far as I have yet had the opportunity of ascertaining. W.E.S. NEUROPTERA. Bittacus australis, Klug. Monogr. Panorp. Berlin Transactions sp. no. 11. Habitat King George's Sound. HEMIPTERA. CHOEROCYDNUS, n.g. Head broad, in front somewhat truncated; ocelli wanting; antennae five-jointed, second joint longest, third, fourth and fifth, somewhat thickened and nearly equal; beak reaching to base of last pair of legs, if not beyond; third joint the longest; thorax in front notched for reception of head, not so wide as the body; scutellum long and pointed, the line separating it from hemelytra very indistinct; hemelytra without a membrane at the end; tibiae very spiny; abdomen broadest behind; tarsi of fore-legs very feeble, two-jointed, second joint shorter than the first, and ending in two claws. Choerocydnus foveolatus, new species. Illustration 23 Insects 6.