Doctrine of Affinity and Analogy. 105 



stance in which it agrees with Pelidnota MacLeay, another 

 South American type,) only the tip is uncovered. The latter, 

 Miniela, has an elevated prosternum, and a metasternum with 

 a very short anterior mucro, so as to leave the mesosternum 

 visible ; whereas in the former, Areoda, the prosternum is not 

 visible without dissection, and the anterior mucro of the meta- 

 sternum is elongated so as entirely to cover and conceal the me- 

 sosternum. The abdomen also in Areoda is covered underneath 

 with an infinity of very minute punctula, which give it a silky 

 appearance ; whereas in Mimela, and likewise Pelidnota, it is 

 laevigated. 



Though Mimela agrees in most of its essential characters with 

 Euchlora, it differs sufficiently to form at least a subgenus in a 

 modern system. In the former the mandibulae have only two 

 teeth at their apex ; in the latter they have three. In this also 

 the body is covered with innumerable impressed puncta of the 

 same size ; whereas in that the puncta are of two sizes, the larger 

 scattered, the smaller almost invisible and quite covering the 

 surface. In Euchlora the last dorsal segment of the abdomen 

 and part of the last but one are uncovered, the very reverse of 

 which, as we have seen, takes place in Miniela. Whether the 

 inner claw of the four anterior legs is bifid at the apex in the lat- 

 ter as it is in the former I cannot say, these tarsi being mutilated 

 in my specimens. 



I shall here mention one very remarkable circumstance, no- 

 ticed by no writer that I have met with, which distinguishes the 

 mandibulae of the tribes of Melolontha F., though less con- 

 spicuous in Melolontha itself than in the Euchlora, Rutelida, 

 AnoplognathidcB, Chalepus, &c. The molary part, or that which 

 appears destined to comminute the food, is an orbicular or 

 subquadrate flat plate at the inner base of the mandibles, 

 scored out into numerous alternate transverse ridges and fur- 



voL. XIV. P rows. 



