62 Trans. Acad. Sci. of St. Louis. 



eyes, enlarged at the posterior end, where two small simple hairs are 

 situated, and extending forward to the anterior tubercle which bears 

 a whorl of bristles like those of the body. A small single pair of eyes 

 situated two-thirds the distance from the dorsal groove to the lateral 

 margin. 



Abdomen not separated from the cephalothorax. Body two-thirds as 

 broad as long, broadly rounded behind. 



Anterior pair of legs fully as long as the body; tarsus of leg I very 

 slightly swollen, two thirds as long as the tibia; tibia not as long as the 

 antepenultimate segment. Second pair of legs three-fifths as long as 

 the anterior pair; third pair slightly longer than the second pair. Last 

 pair of legs extending one-half their length beyond the posterior margin 

 of the body; tarsus one-half as long as the tibia, not swollen; tibia 

 slightly longer and narrower than the antepenultimate segment. All 

 the legs clothed with hairs similar to those of the body. 



Length, 1.68 mm.; breadth, 1.00 mm. 



In moss. Collected by L. M. Smith at Marion, 111. 



Trombidiidae. 



Last segment of palpus transformed into a thumb, penultimate ending 

 in one or two strong palpal clavv's; cephalothorax small and frequently 

 partially concealed by the protruding of the anterior part of the abdo- 

 men; eyes stalked; tarsi frequently swollen. Larvae parasitic upon 

 insects. Adults usually predaceous. 



Trombidium Fabricius. 



Includes forms in which the palpus ends in a single stout claw. 



Two species. 



KEY TO SPECIES. 



Body black, with the legs red T. subnigrum. 



Body and legs red T. missouriense. 



Troinbidiuiu siibnijj;rinn n. sp. 



PL IX. f. 15. 



Alcoholic specimens very dark brown; legs lighter. 



Palpi about one-half as long as the anterior pair of legs; palpal claw 

 long, stout and sharp; thumb of palpus not swollen and slightly surpas- 

 sing the claw. With a double pair of eyes, two being situated on a 

 single, short stalk on each side of the cephalothorax just above the 

 anterior pair of legs. Just in front of the eyes is situated a transverse 

 row of four straight, subequal bristles about twice as long as the eye 

 stalks. 



Body broadest at the anterior end and narrowest at the posterior end; 

 subtruncate posteriorly and very sparsely clothed with simple hairs. 



Anterior pair of legs slightly longer than the body; tarsi swollen and 

 thickly clothed with fine hairs, somewhat shorter than the tibia; tibia 

 slightly longer than the antepenultimate segment. Second and third 



