106 Mr. KiRBY on Mr. W. S. MacLeay's 



rows*. When the mandibles are open, the food, after it has 

 been divided by their apex, must pass between these plates, 

 which, supposing that the ridges of one mandible are received 

 by the furrows of the other, as is most probably the case, must 

 have vast force in comminuting the food, not so much by the 

 friction of the plates, since that could scarcely take place in 

 consequence of the above structure, but from their pressure and 

 the action of the sharp ridges. The mandibula indeed is parti- 

 cularly fitted for this double office, the upper part being thin 

 and adapted to cuttingt, and the base vastly thick and strong, 

 as if its office was great pressure :|;. At the base of the mandible 

 in the genus before us, but not in all, there are other short fur- 

 rows forming an acute angle with the transverse ones and open- 

 ing into the gullet. In the Dynastida MacLeay, the molary 

 space is visible, but is smaller, and has fewer furrows. In Dy- 

 nastes Enema it has only two obtuse ridges and as many furrows, 

 and appears evidently calculated to masticate, but more grossly, 

 a harder substance than what is submitted to the action of the 

 mandibles of Melolontha F. In a specimen of Areoda I found 

 adhering to this molary plate a substance resembling the pollen 

 of flowers, which may hence be conjectured to be the food of 

 that genus §. 



From this account it seems I think evident, that a modification 

 of the three kinds of teeth of vertebrate animals is to be found 

 in these tribes as well as the Orthoptera, in which Marcelle de 

 Serres detected them ; for we find the incisores at the apex of the 

 mandible, the molares at its base, and the laniarii at the apex of 



* Tab. III. Fig. 4. c, b. t Ibid. a. % Ibid. b. right hand figure. 



^ Since this paper was written, I met accidentally with a passage in Cuvier's Ajia- 

 tomie Comparee (iii. 321 — .), by which it appears that he had observed in the mandibles 

 of the larvffi of the Lucani " vers lew base, uiie surface molaire plane et stride ;" but he 

 does not appear to have noticed this structure in any perfect insect. 



the 



