347 



Abdomen never with a chitin- Abdomen sometimes with a 



ous hood-like projection from its chitinous hood-like projection 



anterior margin. from its anterior margin. 



Claws of legs usually small and Claws of legs always stout; if 



monodactyle ; if tridactyle the tridactyle the dactyles are snb- 



dactyles are usually unequal. equal. 



* 



When we consider all these points of difference, it appears 

 to us that they are not only of sufficient importance for the 

 separation of the two forms into different families, but that 

 they might even justify a wider separation and a higher rank. 

 About the only important characters the two have in common 

 are the chitinous integument and the presence of the pseudo- 

 stigmata and the pseudostigmatic organs. Mr. Banks, in his 

 treatise on "The Acarina, or Mites" (Proc. U. S. Nat. Mus., 

 Vol. XXVIII., p. 1-114), separates those forms which have the 

 cephalothorax hinged to the abdomen from the other oribatids, 

 under the family name of Hoplodermidce. This separation 

 and name the author of this paper has adopted. 



Mr. Michael's separation of those forms which possess ab- 

 dominal wings from those which do not ("Apterogasterea") we 

 accept, raising both forms, however, to family rank, and giving 

 the first-mentioned the old name Oribatidce, since it contains 

 the old genus Oribata. This division is not altogether happy 

 for two reasons: first, many authors may consider the small, shelf- 

 like chitinous expansions from the shoulders of the abdomen 

 in the case of some genera (as Notaspis and Tegeocranus) as 

 homologous with the true abdominal wings, or pteromorphse; 

 second, there are not many other fundamental characters in 

 support of the division. Notwithstanding these facts, we con- 

 sider the development of abdominal wings — especially when 

 taking into account their defensive value and the habits of mites 

 possessing them, and some other points of difference as well- 

 as of sufficient importance to entitle such forms to family rank. 



Since we have applied the family name Oribatidce to those 

 forms having abdominal wings, the remaining forms, the "Ap- 

 terogasterea", we naturally consider as constituting a family, us- 



