4>60 EXTERNAL ANATOMY OF INSECTS. 



when you find, that in certain tribes such commutations 

 of organs and their use take place. 



The following is the structure, as to its organs, of the 

 mouth of the myriapods, as exhibited by the centipedes 

 (Scolopendrides). The part which appears to perform the 

 office of the upper lip (but which M. Savigny regards 

 as the nose, calling it the chaperon,) is a transverse piece 

 with a deep anterior sinus, in the centre of which is a 

 minute tooth a . This piece is separated from the fore- 

 part of the head by a suture; but it probably is not move- 

 able: however, it covers the mouth, and may be regarded 

 rather as analogous to the labrum. Below this are two 

 mandibles, armed at their end with five sharp triangular 

 teeth 5 , under which are the maxillce, terminating in a 

 moveable concavo-convex lobe, resembling the valve of 

 a bivalve shell c ; and between them is the labium, of a 

 rhomboidal shape, divisible into two lobes, attached la- 

 terally to the maxillae : these lobes M. Savigny terms the 

 second maxillae, forming with the others, according to 

 him, the labium d . Affixed to the base of this labium, or 

 covering it on the outside, are a pair of pediform palpi, 

 which he considers as the first auxiliary labium, and re- 

 presentative of the first pair of legs of hexapods and Iuli e . 

 I imagine them to be also the analogues, in some degree, 

 of the labial palpi of a perfect mouth. The last of the 

 organs in question is a large rhomboidal plate affixed to 

 the first apparent segment of the trunk, crowned at its 

 vertex with two truncated denticulated teeth, and from 



3 Anim. sans Vertebr. I. i. t. W.f. 2. a. a'. 



b Plate VII. Fig. 13. c'. « Ibid. d'. 



d Anim. sans Vertebr. I. i. 10G. Plate VII. Fig. 13. b'. 



e Ubi supr. 45 — . 



