480 BRITISH OEIBATIDiE. 



mediate species to TIermannia on the one side and to 

 Hypochtlionlus on the other ; as to the latter genus, it 

 is easy to make a sharp distinction, because the seg- 

 mented abdomen of HijjJocJdhonms is not found in the 

 adults of any other genus in the family, although 

 indications of it may sometimes be seen in the very 

 young larvae. It is not by any means so easy to find 

 any sharp dividing line between Hermannia and 

 Nothrus, although such forms as Hermannia jpicea and 

 Nothrus spiniger are extremely diflPerent ; the real dis- 

 tinction lies mainly in the flat or concave notogaster 

 and more or less oblong or shield-shaped abdomen of 

 Nothrus, as compared with the arched notogaster and 

 rounded abdomen of Hermannia. In treating of the 

 last-named genus (page 439) I have already given my 

 reasons for my distribution of the species between the 

 two genera, and for being unable to agree in that of 

 Berlese, and I will not repeat them here. Prof. Berlese 

 seeks to overcome the difficulties of the typical and 

 intermediate forms by erecting the latter into a sub- 

 genus, which he calls Angelia. I do not think that it 

 is desirable to follow this suggestion, in the first place 

 because named sub-genera are inconvenient, and in 

 the next place because it appears to me to double 

 the evil, as it does not render it any easier to distin- 

 guish between Angelia and Hermannia than it was 

 between the old Nothrus and Hermannia ; and there is 

 the new difficulty of distinguishing between Nothrus 

 and Angelia, which Berlese does not seem to me to 

 solve in any satisfactory manner. 



There are probably few, if any, genera among the 

 Orihatidoi in which it is more difficult to ascer- 

 tain which are entitled to be treated as species and 

 which as varieties than the present. The immature 

 stages are very like the adults ; and consequently, in 

 closely-allied species, very like each other, and thus do 

 not afford as much assistance in this respect as those of 

 most other genera. Taking as the best example the 

 four species N. horrldus^ N. hiverrucatuSy N. blcari- 



