DYNASTIN/E 253 



together with Bothynus, might very well constitute a distinct 

 tribal group by themselves. Here, the head has an obtuse apex 

 having a bilobed transverse erect plate as in Orizabus, except that 

 the plate is apical and not post-apical, and the vertex in the male 

 bears a long erect horn, which is reduced to a small tubercle in the 

 female. The thoracic modifications are also of an entirely different 

 kind, there being an abrupt slope in about apical half in the male, 

 but without any indication of corniform processes; in the female, 

 the pronotum is perfectly even, again as in Orizabus. The small 

 lamellate, almost completely hidden, externally obtuse and non- 

 dentate mandibles are also nearly as in Orizabus, and in fact there 

 is a markedly close affinity between these two genera. So great is 

 this resemblance that it is small wonder that the female should 

 have been described recently as a female Orizabus, especially as the 

 hind legs, excepting the feeble apical crenulation, the hind tarsi, 

 with their obliquely extended basal joint and the tridentate anterior 

 tibiae are almost exactly as in that genus. The very deep concavity 

 at the base of the mentum is however a conspicuous distinguishing 

 character in Xyloryctes. The pygidium does not differ much 

 sexually, but in the male there is usually visible a small tubercular 

 swelling, just above the centre of the disk, that is never seen in the 

 female; the upper marginal line is always arcuate in both sexes. 

 The propygidium is covered throughout with small close-set sub- 

 asperate punctures and the transverse strigilation of the Strategid 

 genera is not observable; stridulation is therefore presumably 

 much less strenuous in Xyloryctes than in Strategics, if it exists at all. 

 Xyloryctes leads almost directly through Heterogomphus from 

 Orizabus to the more typical Oryctids, and through Orizabus and 

 Aphonus to the typical Pentodontids, showing rather conclusively 

 that there is no marked distinction in real physiological structure 

 between these two tribes. As in Orizabus, there is in Xyloryctes 

 no progressive series of degradational forms in the male, as there is 

 in Strategus, that sex being as constant in general form as the female, 

 except that the cephalic horn varies somewhat in length and thick- 

 ness, though not to very marked degree. The species are moder- 

 ately numerous, those represented before me being the following: 



Pygidium (cf) shorter, strongly transverse, having numerous rather 

 close-set fine punctures throughout 2 



