AMERICAN APTERA. 409 



Key to genera described in this paper. 



1. Abdomen with some large spatulate bristles on the dorsum. 



Pelops 

 Abdomen withot spatulate bristles 2 



2. Tarsus of leg one broadened distally GymnobateS 



Tarsus of leg one tapering distally 3 



3. Lamellae narrow, attached to the dorsal surface of the cephalo 



thorax by their inner margins Oribata 



Lamellae very large, attached to the dorsal surface of the cephalo- 

 thorax by their posterior margins only Oribatella. 



Gen. PELOPS C. L. Koch. 

 Some of the setae on the dorsum of abdomen large, spatu- 

 late ; integument frequently rough ; mandibles broad at the 

 base but suddenly becoming narrow and terminated by minute 

 chelae. A large rectangular projection from the anterior mar- 

 gin of the abomen usually present. 



One species. 



Pelops latipilosus. n. sp. 

 (Plate XV., Fig. 12.) 



Chestnut brown ; integument slightly rugose. 



Cephalothorax small, the posterior part hidden by a rectangular pro- 

 jection from the anterior margin of the abdomen. Lamellae almost as 

 long as the cephalothorax, about one-half as broad as long, the outer 

 margin strongly convex, the inner free margin strongly concave; trans- 

 lamellae a mere ridge; lateral lamellae present, similar to the lamellae 

 in shape but longer. There is a large, stout pair of tectopedia present 

 for the protection of the first pair of legs. The cephalothorax bears two 

 pairs of prominent bristles; a large, long, lanceolate pair situated on 

 the posterior dorso-lateral aspect, which are almost as long as the 

 cephalothothorax itself, directed forwards and curved towards the 

 median plane ; and a much smaller, slightly curved serrated pair 

 situated on the sides of the rostrum ; directed outwards. Pseudostig- 

 matic organs about as long as tibia of leg one, clavate with rugose 

 heads. 



Abdomen fully two-thirds as broad as long ; pteromorphae one-half 

 as long as abdomen, truncate in front. When the mite is walking the 

 pteromorphae are so expanded as to present a view of their whole 

 external surface from above, but upon the slightest provocation they 

 are instantly drawn in close to the body and then entirely hide the legs. 

 There is a broad, rectangular projection extending from the anterior 

 margin of the abdomen, from each anterior corner of which projects 

 an enormous, spatulate bristle, fully as long as the cephalothorax 

 and projecting beyond the tip of the rostrum ; at its broadest part 



TRANS. AM. ENT. SOC, XXXV. (52) NOVEMBER, 1909 



