440 BRITISH ORIBATID^. 



strongly arched notogaster, as contrasted witli the oblong 

 orrliomboid abdomen, truncated posteriorly, of iV^ofAr^i^-, 

 with its raised edges to the notogaster and its central 

 portion depressed, or only slightly raised, is the true 

 distinction, and practically divides the two into natural 

 groups. Berlese has attempted to define the difference 

 between the two genera,* but I confess that he seems 

 to me to have been singularly unfortunate in his results; 

 nor can I think that his method is justified by the 

 practice of zoologists ; indeed I believe that it would 

 cause great confusion if it were adopted. He states that 

 the reliance upon tridactyle and monodactyle claws 

 should be abandoned, in which I quite agree with him ; 

 but he proceeds to say that there are not any differ- 

 ences between Nothrus and Hermannia except two, viz. 

 1st, that in Nothrus the body has a prismatic, and in 

 Hermannia a globose form ; 2nd, that in Nothrus the 

 genital aperture is near the anal, and in Hermannia 

 these apertures are distant from each other. Having 

 thus entirely altered Nicolet's definition of his genus, 

 Berlese says that Nicolet's type species of Hermannia 

 is a Nothrus and not a Hermannia, and quietly transfers 

 it to Nothrus. This would upset the whole of the good 

 that Nicolet did in dividing the last-named genus, and 

 leave matters in worse confusion than they originally 

 were ; because H. picea, the species transferred, is most 

 distinctly a creature which should be classed with H. 

 arrecta and H. granulata (a foreign species), and which 

 apparently is only separated from them because the 

 genital and anal plates are rather nearer together in 

 picea than in the other two species. This character of 

 the distance between the genital and anal plates is one 

 which I considered very carefully when I was forming 

 my own classification of the family. I had hoped to 

 utilise it in defining genera, but the result of my in- 

 vestigation was that I felt compelled to abandon that 

 idea, becoming convinced that this character had only 

 a specific value. Possibly a better instance of this 



* '• Acari, &c. Ital.," Notes, fasc. iii, p. 4. 



