THE INTER-COXAL LOBE OF CERTAIN CRAYFISHES. By W. J. Mackay, B.Sc. I have been enabled to make the observations embodied in this note, at the Biological Laboratory of the Sydney University, through the kindness of Dr. Haswell, whom I have to thank for having directed my attention to the subject, and for having sup-plied ine with the requisite materials. In a figure of the branchial region of Astacopsis Ffanklmii,. in Huxley's paper ' On the Classification of the Crayfishes,'*" there are represented certain appendages connected with the branchiae, though there is no reference to them in the text, nor has attention, as far as I can ascertain, been specially directed to them. These appendages in the case of Astacopsis serraius, and the same holds good of A. bicarinatus, are visible before the removal of the branchiostegites, provided the animal be turned sternal side uppermost and the legs separated. They may then be seen as triangular-shaped bodies lying under the edges of the branchiostegites, and attached to the posterior faces of certain thoracic limbs. On i-emoving the branchiostegites the appendages are pai'tly hidden fi'om view by the bases of the podobranchise; but on these being tui-ned aside they are seen to be behind and below the anterior arthrobranchiai, and perpendicular to and below the posterior arthrobranchiae ; each of them being attached by a small neck to the membrane which, arising from the posterior aspect of the coxopodite, reaches to the epimeron above, and behind is attached to the arthrophragm of the particular limb. Examined more closely, the upper portion of the anterior face of one of these bodies, which may be called the inter-coxal lobes, is alone united to the arthrodial membrane ; while the lower surface of the anterior face is applied to the base of the coxopo-dite, which is smooth and convex. •P.Z.S., 1878. p. 765.