DYNASTIN^E 223 



and the only American Pentodontid having the pronotum differently 

 modified sexually, but its affinities are so clearly in harmony with 

 Ligyrus in certain habital features, that it cannot be placed among 

 the Oryctini under the present definition of that tribe. Its com- 

 ponents have been the source of much confusion and misconception 

 since the original species was described by LeConte under the name 

 Aphonus clunalis, which, however, he correctly surmised was not 

 its proper generic position. Then G. H. Horn described two species, 

 apparently without suspecting that either had any close relationship 

 with clunalis Lee., an unexplainable oversight. Finally, as stated 

 above, the genus was confounded with the Australian Cheiroplatys 

 by Bates, because of a number of suggestive resemblances. The 

 largely unwarranted synonymy, not only here but in Ligyrus, 

 introduced by Mr. Bates, caused that author to unite two distinct 

 genera, as on plate 18 of the Biologia, figure 23 is said to represent 

 the male of Cheiroplatys fairmairei, though it can plainly be seen 

 to be a Pseudaphonus allied to pyriformis Lee., which was originally 

 described as an Aphonus, the genus differing radically, among other 

 ways, in having no trace of sexual modifications of the pronotum 

 and in its very small head; figure 24 is said to be the female of 

 fairmairei, which it evidently cannot be, but is the female of a 

 true Orizabus, the female in Aztecalius being strongly pyriform; 

 nor does figure 20 represent the female of a species in any way 

 closely allied to cultripes, correctly depicted in figure 19; the legend 

 at the bottom, referring to figure 20, evidently .should be 9 and 

 not " cf " One curious result of all this confusion is the fact that 

 the largest and bulkiest species of Orizabus yet discovered, and 

 apparently the most abundant of all, is still without a name. The 

 trouble is due in some measure to the close mutual resemblances, 

 not only between species but between genera in this part of the 

 tribe. That true species bear these mutually close inter-resem- 

 blances can be demonstrated by the ample series which I have taken 

 time to bring together; it is only by comparing series that specific 

 differences become obvious in many cases. 



There are two rather distinct subgeneric groups in Orizabus, 

 which may be defined as follows: 



Front centrally tuberculate; clypeus arcuate at tip, the post-apical carina 

 bilobed; female similar in general form to the male, the latter having 

 the anterior tibiae evenly arcuate externally, the female tridentate. 



Group I 



