of the less-knotvn groups of Lctmcllicom Coleoptera. 483 



Phytojphaga, etc., but so far as I know they are not found 

 in any other Lamdlicornia. 



The distribution of the Achpinae is exceedingly inter- 

 esting. Until recently only three species have been 

 recognized, but although difficult to distinguish they will 

 have to be considerably multiplied. Aclopiis is peculiar 

 to South America, while Phaenognatha consists of various 

 Australian species (all but one of them described later in 

 the present paper), and one or more from South America 

 so closely related to them as to be quite fittingly placed in 

 the same genus. 



The proper systematic position of the remarkable 

 Californian genus Plcucoma has been the .subject of a 

 prolonged controversy, and its structure has been pretty 

 thoroughly investigated. Leconte and Horn claimed it 

 as an undoubted Laparostict allied to the Geotrtipinac ; 

 while Gerstaecker placed it with equal confidence in the 

 Pleurosticti near Pacligpus. The latter writer was wrong 

 in declaring the spiracles to be situated in the chitinous 

 rings ; but I believe his view of the affinities of the genus 

 was not altogether unjustified, and that although the two 

 theories quoted above appear quite irreconcilable, it is 

 not necessary to entirely reject either. I believe both 

 Pleocoma and Pacliypns to be among those ancient sur- 

 vivals which are destructive of all clear-cut systems, but 

 which throw most valuable light upon phylogeny. Dr. 

 Horn has himself pointed out that Pleocoma has the 

 spiracles so placed as to make it doubtful whether it is 

 Laparostict or not. They are indeed surrounded by 

 membrane, but so placed as to appear as though this 

 encroached upon the horny segments. Both Pleocoma 

 and Pachypus have the very un-Melolonthine feature of 

 possessing a horn in the male sex, the former upon the 

 head and the latter upon the thorax ; but both have also 

 the entirely Melolonthine characteristic of a many-leaved 

 anteunal club. The number of joints in the club is 

 invariably three in the whole of the Scarahaeidae, except 

 in many Mclolonthinac and these two genera. On the other 

 hand, Pleocoma appears to have very little in common 

 with the Geotrupinae, except the total number of eleven 

 joints to the antenna, which if there were any similarity 

 in these organs themselves would certainly be a very 

 important fact, for this number of joints, general in other 

 Coleoptera, occurs in no other Lamellicornia so far as 



