670 EXTERNAL ANATOMY OF INSECTS. 
vots: at the same time the mola or head of the latter 
joint, which has often a flexure so as to form an elbow 
with the rest of it, inosculates in the gonytheca, and is 
also suspended by ligament to the orifice through which 
the muscles, nerves, and bronchize are transmitted: so 
that in fact the articulation, strictly speaking, belongs 
exclusively to none of the kinds observable in vertebrate 
animals, but partakes of several, and may properly be 
denominated a mixed articulation,—a term applicable in 
numerous instances also to the other articulations of the 
legs of insects. In the different Orders some variations 
in this respect take place,—I will notice some of the most 
remarkable. In no Coleopterous insects is the structure 
more distinctly visible than in the larger Lamellicorns. 
In Copris bucephala, for instance, if you divide the thigh 
longitudinally, you will find on each side, at the head, 
that it is furnished with a nearly hemispherical protube- 
vance, perforated in the centre for the transmission of 
muscles, and surrounded externally by a ridge, leaving 
a semicircular cavity between them*: if you next exa- 
mine the ¢ibia, after having extracted it, you will find 
on each side, at the base, a cavity corresponding with 
the protuberance of the thigh which it receives, having 
likewise a central orifice, and surrounded by a semicir- 
cular ridge corresponding with the cavity in the thigh 
in which it acts: below this ridge another cavity, form- 
ing a small segment of a circle, receives the ridge of the 
thigh®. You will observe that the ridge of the ¢zbza re- 
presents the lateral condyle lately noticed: in the Dy- 
nastide this is more prominent, and often forms a smaller 
a Prate XXVII. Fic. 1). 7”. > Ibid. Fic. 10, ¢’”. 
