Tkombidiidae 



Tromhidium 2 species 



54 Trans. Acad. Sci. of St. Louis. 



In this paper 32 species are described, which are dis- 

 tributed in 14 genera and 7 families. The arrangement 

 into genera and famihes is as follows: 



Cheyletidae Gamasidae 



Cheyletus 1 species. Hyletastes 1 species. 



Gamasus 3 species. 



RHYNCHOLOPHIDAE UEOPODIDAE 



Rhynckolophus 9 species. Uropoda 5 species. 



S^«^^« 1 species. Uroseius 1 species. 



Dinychus 1 species. 



Oribatidae 

 Oribata 1 species. 



Gamasidae Tyroglyphidae 



Macrocheles 2 species. Tyroglyphus 1 species. 



Laelaps 3 species. Rhizoglyphus 1 species 



description of species and higher groups. 



Cheyletidae. 



Body divided Into cephalothorax and abdomen; last segment of palpus 

 transformed Into a papilla, while the penultimate ends in a large claw; 

 without eyes; leg I ending in several long hairs. Usually predaceous in 

 habits, but sometimes parasitic. 



Cheyletus Latreille. 



Body longer than broad but never twice as long as broad; palpi 

 swollen on the outer side near the base; hind legs provided with claws; 

 papilla of palpus having at least one specialized comb-like bristle. 

 Seldom parasitic, generally predaceous. 



One species. 



Cheyletus longipalpus n. sp. 



PL VIII. f. 1. 



Light orange; legs and palpi lighter than the body; integument 

 coarsely granular. 



Cephalothorax slightly larger than the abdomen and possessing four 

 rows of large, pectinate, fan-shaped scales; two rows of five scales 

 each near the median line and two lateral rows of four scales each. 

 Total length of the beak almost equal to the length of the rest of the 

 cephalothorax; beak with a base much swollen dorsally and possessing 

 a pair of small, straight bristles near the tip on the dorsal surface and 

 a similar pair situated laterally to these. Palpi long, being a third 

 longer than the beak. First segment of palpus small, disc-like; second 

 segment enormous, long, curved, about equal to the total length of the 



