54 FAMILIES OF PETALOCERA WHICH LIVE 



articulum secundum productis, paululum extus 

 arcuatis, fimbriatis. 



Mentum crustaceum, suhquadratum, profundi emargina'- 

 turn. 



Caput subsemicirculare ; cli/peo scepe dentato, interdum 

 cornuto. Corpus orbiculato-ovale, convexum vel 

 depressum; ahdomine brevi, elytris haud obtecto. 

 Thorax transversus ; scutello rarissime distincto, 

 subtrigono. Pectus magnum, ideoque femora 

 intermedia ad basin late dispartita. Pedes va- 

 lidi, unguibus minimis ; tibite, anticcz extrinsecus 

 3-dentat(Ef apice calcare uno instruct (B, tar sis 

 exiguis, in quibusdam nbsoletis ; libicz medics, 

 apice l-calcaratcRy postice calcare uno instructa. 



Observations. 



The Scarabmd(Z occupy a most important place in the 

 economy of nature, and possess so very distinct a form 

 that they are only likely to be confounded with the Apho- 

 diida ; from these, however, they may be distinguished by 

 their elongate lanceolate mandibles and large pectus. 

 Several genera of the Scarabaidce, — such as Onitis, Ontho- 

 phagus, &c. — approach so nearly to Aphodius, that here, 

 as in most cases where families meet, it will be found most 

 difficult if not impossible to draw the line of demarcation. 

 There is less likelihood of confounding them with the 

 Geotrupida, because, though several insects in both fami- 

 lies evidently approach to one another in general form and 

 structure, yet none that I have yet seen can accurately be 

 said to fill up the iaterval that occurs between the cor- 

 neous porrect mandibles of the one family, and those 



