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. 



