EXTERNAL ANATOMY OF INSECTS. 597 



pleura, the base and apex, the angles, and the hypoderma. 

 At first it should seem as if an elytrum was not like other 

 wings divided into areas; but I think upon examination 

 it will be found that, though often nearly obsolete, these 

 are represented in it; for the epipleura a with the recurved 

 part of the external margin seems to me analogous to the 

 Costal Area; the inflexed part adjoining the scutellum and 

 often going beyond it to the Anal, and the rest of the organ 

 to the Intermediate. All this you may see in the dung-cha- 

 fer, Geotrupes stercorarius. The axis b or pivot by which 

 the elytrum articulates with the trunk is generally placed 

 about the middle of its base, but nearer the scutellar 

 than the humeral angle, and varies in length and shape 

 in the different tribes, but not so as to merit particular 

 notice ; it may be regarded as composed of three parallel 

 pieces, one belonging to each area, that of the costal be- 

 ing the longest. In many these pieces are marked by no 

 line of distinction, but in Macropus, &c, they may be readi- 

 ly traced c . The suture d is the internal margin of the 

 elytrum from the point of the scutellum to the end. In 

 many beetles the right hand suture, looking from the 

 anus to the head, has a lower ledge or margin, and the 

 other, one more elevated, which when they are closed 

 lies upon the former ; in some Dynastidce there seems a 

 kind of ginglymous structure in this part, each suture 

 being fitted with a kind of ridge which is received by 

 a channel of the other ; in these the suture is generally 

 marked out by an adjacent channel : but the most re- 

 markable structure of this part distinguishes the genuine 

 species of the genus Chlamys, in which both the sutures, 



3 Plate XXVIII. Fig. 6—8. d'" . >• Ibid. Fig. 3—5. b'". 



• Plate XXVIII. Fig. 3. d Plate X. Fig. 1. c" . 



