EXTERNAL ANATOMY OF INSECTS. 665 



ing lobes or condyles ; that on the inner side being the 

 smallest and shortest, and constricted just below its apex; 

 and that under this is a shallow or glenoid cavity, ter- 

 minating posteriorly in a lubricous flat curvilinear ridge. 

 If you next examine the trochanter in articulation with 

 the coxa, you will perceive that the head of the former 

 inosculates in it, that the lower condyle is received by a 

 sinus of the coxa, which also has a lubricous very shallow 

 cavity corresponding with the ridge, in which it turns ; 

 and in the head of the coxa, on the lower side, is an ex- 

 ternal condyle, which is received by a sinus common to 

 both, of the head of the thigh and of the exterior side of 

 the trochanter 3 , in which it likewise turns: this last con- 

 dyle has also an internal protuberance, which appears to 

 ginglymate with a cavity of the trochanter : from this 

 structure the leg is limited chiefly to a motion up and 

 down upon two pivots, or to fold and extend itself You 

 will find an articulation very near this, but on a smaller 

 scale, in the stag-beetle. In the other kind of articula- 

 tion, which admits of freer motion, the head of the tro- 

 chanter is prolonged, and the process terminates in a 

 short interior condyle, which appears to work in a cor- 

 responding cavity of the interior of the coxa ; and the 

 base of the process is encompassed by a ridge with a 

 cavity behind it, which is received by another of the 

 lower part of that piece, and admits a corresponding 

 ridge — a structure that allows a rotatory motion. In the 

 hind-legs of this tribe the motion is chiefly limited to 

 folding and extending ; in Carabus, &c, also the head of 

 the trochanter is nearly hemispherical, and the articular 



« Plate XXVII. Fig. 12. b. 



