1917] Synopsis of Beetle Mites 119 



BB. Abdomen divided into areas dorsally by grooves or sutvires making it 

 appear segmented; integument usually poorly chitinized. . Hypochthonidae 

 C. Dorsal sutures of abdomen oblique; segments of legs inflated . .Trizetin.'E 

 CC. Dorsal sutures of abdomen transverse; segments of legs not inflated, 



Hypochthonin-^; 



AA. Cephalothorax hinged to abdomen; tracheae absent Hoplodermatidae 



B. Abdomen divided into parts, as if segmented, by transverse grooves or 



sutures Protoplophorin^ 



BB. Abdomen not divided into parts, as if segmented, by transverse grooves 

 or sutures. 

 C. Genital and anal openings situated in a large ventral plate which is 



anchylosed to dorsal plate Mesoplophorin^e 



CC. Genital and anal openings not situated in a large ventral plate, anchylosed 

 to dorsal plate Hoplodermatin.e 



These fourteen subfamilies contain many genera; especially 

 is the subfamily Oribatince rich in genera. I have tried in the 

 following pages to key out as many of the genera of the very 

 large number proposed as appeared to be based upon good 

 characters, and to be acceptable from the standpoint of nomen- 

 clature. However, a few genera appear to be good, that I have 

 not been able to place in my keys, because of incomplete data 

 on their generic characteristics. Many proposed genera will 

 not be found in my keys. For varioiis reasons some twenty- 

 four of these have been excluded. Some were founded upon 

 characters which I regard as purely specific; others are almost, 

 if not exact, synonyms of older genera; others have names 

 which are preoccupied; and yet others have been rejected 

 for various reasons not here mentioned. 



In the keys which follow, readers will find given with each 

 genus the name of its author, the date of its establishment, and 

 the name of its type species. Lack of space forbids a dis- 

 cussion of taxonomic points involved in the fixing of some of 

 these types. In a few cases these will be given briefly in 

 footnotes. 



Family Oribatid^. 



Key to the Genera of Subfamily Pelopince. 



a. Abdomen with a shelf-like expansion extending forward from its anterior 

 margin over the base of the cephalothorax. 



b. No true lamellae or translamella present Pelops Koch, 1835 



[Type: P. acromios (Hermann)] 



bb. Lamellae, and frequently translamella present Euplops n. gen. 



[Type: Pelops uraceiis Koch] 

 aa. Abdomen without shelf-like expansion at its anterior margin, 



Peloptulus^ Berlese, 1908 

 [Type: Pelops phaeonotiis Koch] 



^Erected as a subgenus by Berlese. 



