S2 REMARKS ON THE LINN^AN GENERA 



longing to the column of Thalerophagous Rectdcera. We 

 shall see there two new genera, which I propose to name 

 Nigidius and Figidus, intervening between the types of 

 the Lncanidtz and Passalidce, possessing the antennte of 

 the former and the general appearance of the latter, with 

 a construction of the mouth which bears evident analo- 

 gies to that of both. A family which I have called Sy7i- 

 desidce is clearly connected with the Passalidce. by the 

 antennae and impressed thorax; while their convex form of 

 body, indistinct maxillae, and short mentum, seem to prove 

 their affinity with Msalus, F. The antenna3 also of this 

 last genus, which I suspect however to be not quite in the 

 circle, approach to those of Lamprima, Lat., which again 

 joins the Lucanidce, and thus completes the circles by 

 means of two new genera, to which I have given die ap- 

 pellations of Ryssonotus and Pholidotus. 



I have not been able to discern much lateral aflS- 

 nity between the corresponding families of Sapropha- 

 gous Petalocera and Thalerophagous Reciicera, except 

 at the extremities of the columns, or, which is the same, 

 at the points at which the circles touch one another. In 

 the construction of the mouth, the JEsalida, St/ndesida, 

 and Passalidce bear no resemblance to the Scarabceidce, 

 Aphodiidce, and Trogidce. Indeed, in proportion as the 

 general plan of construction differs, it is clear that we 

 ought not to expect much affinity in the details. Thus 

 a very conspicuous analogy may and does exist between 

 the two columns of Petalocera, and even between the 

 two columns of Rectdcera, which by no means can be ex- 

 pected to be so distinct between a Recticerous and a 

 Petalocerous column. 



Nevertheless it appears to be a law of Nature never to 



