38 On tie Classification o/Oribatidas. 



not out of the Arthropoda — it is, " head, protothorax (s<c), and 

 metathorax separate." I do not think it would Le desirable 

 to revive this genus. 



Dr. Oudemans says that "the Oribatei wait for a thorough 

 revision," and he gives instances. He says that members of 

 the genus Nothrus are said tahave three claws, but that he 

 has species with one. I think that the tridactyle claw as 

 part of the definition of the genus has long been abandoned ; 

 he will find three monodactylc species described in my 

 'British Oribatidje' in 1888. Tlien he says tliat "amongst 

 the species of Koch belonging to the genus Oribates there 

 are several of which the wing-like expansions are not mov- 

 able and do not protect the legs." Many of the ptero- 

 morphas are only slightly flexible, very few are, strictly 

 speaking, movable ; but Koch's species without them have 

 been removed from the genus by, I think, all modern 

 acarologists. Then he says that " many Eremceus have no 

 arched abdomen, but a hollow one " ; he will find in my 

 definition of the genus, in 1888, " Notogaster arched or 

 concave in the centre." Then there are some remarks about 

 the similarity of the nymphs of Leiosoma and Cepheus, and 

 he suggests that the genera should be joined. If he refer 

 to my work so often quoted above he will find that they 

 practically are joined, but I feel doubts whether they will 

 not have to be separated again ; and if Dr. Oudemans 

 endeavours to classify the Oribatidge by the hairs on the 

 nymphs, 1 fear he will find that he must neglect important 

 structural difierences in the adults. Finally, Dr. Oudemans 

 says, in effect, that the anterior portion of an Acarus cannot 

 be called a cephalothorax because some of the creature's legs 

 are abdominal : I regret to say that 1 fail to appreciate the 

 cogency of this argument. 



It will be seen that the above remarks are written in the 

 spirit that it is better not to make changes in well-known 

 names unless it is unavoidable. 



Now a few words as to the species in the list. There are 

 40 named species; of these three, viz. NotJa-us jmUcns, Koch, 

 Zetes epinppiatus, Koch, and Zeies fuscomaculatus^ Koch, are 

 founded upon immature (nymphal) forms. lloplophora 

 lucida^ Koch, is one of the many synonyms of lloplophora 

 dasyyus^ DugJis. //. nitens^ Kic, is stated to be equivalent 

 to h. dasi/pus, Clapariidc, but not to JI. dasypus, Dugbsj 

 but Clapaiiide only quotes Dugiis and does not use the name 

 dasypus at all, he uses contractilis. No reason is given for 

 saying that il. nitens, Nic, is not the same as //. dasypus j 

 Duges ; Nicolct said it was, and I do not know of any reason 

 for disagreeing with him. Five species of Leiosoma are 



