52 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



199) with a pnir of approximate subclavate rods subtended by a 

 thick chitinoiis ridge. Fourth antennal segment without special 

 olfactory setae. Unguis (pi. 19, figs. 200, 201) simple, untoothed. 

 Unguiculus extending one-half (first pair) to two-thii'ds (third pair) 

 as far as unguis, broadly lanceolate, acute, untoothed. Knobbed 

 tenent hairs one, two, or none (see beyond). Abdominal segments 

 without ankylosis. Fourth abdominal segment one-fourth longer 

 than the tliird. Furcida appended to the fourth abdominal segment, 

 short (not reaching the ventral tube), but variable in length, extending 

 to the middle of the third abdominal segment or to the middle of the 

 second. Manubrium usually longer than dens (as 9:7), sometimes 

 equal to dens, stout (pi. 19, fig. 202), with a pair of stout ventral 

 subapical setae and many smaller dorsal setae. Dsntes (pi. 19, fig. 

 202) stout, not tapering, with five or six (as many as 10 in large 

 individuals) dorsal crenulations near the middle. Mucrones (pi. 19, 

 figs. 203-206) slightly shorter than hind ungues, elongate, triden- 

 tate; apical tooth slender, almost straiglit or slightly hooked; second 

 tooth suberect; third subequal to second, or smaller, lateral in 

 position, inchned caudally. Rami of tenaculum (pi. 19, fig. 207) 

 quadridentate; corpus wdth one strong carving ventral seta (the 

 number varying, however, from one to four). Clothing of minute 

 stifi' simple setae, with short erect simple sensory setae. Integument 

 smooth. Length, 0.9 mm; maximum, 1.3 mm. 



Variations. — Specimens from Pennsylvania that I studied had a 

 black body pigment in the form of minute points, outlining the hypo- 

 dermis cells. 



The eyes, particularly of small individuals, may be pigmented 

 separately, instead of occupying a common pigment spot on each side 

 of the head. 



In small specimens the antennae may be slightly shorter than tlie 

 head. 



The tliird antennal segment is sometim.es shorter than the second. 



The tibiotarsus has occasionally a distal subsegment. 



In addition to the five or six dorsal crenulations near the middle 

 of the dens, there are several smaller and less evident folds. 



The variation in the mucro occurs chiefly in respect to the lateral 

 tooth, which varies mostly in size and form, though slightly in posi- 

 tion. In an occasional specimen this tooth is present on one mucro 

 but absent on the other. 



I have seen but one ventral seta on the tenaculum, though the 

 number varies from ore to four, according to Linnaniemi. 



The typical form of minuta has no tenent haii's (Axelson, Borner). 

 Some of my European specimens have no tenent hairs; others have 

 two or even three; this being true of North American specimens also. 

 The second tenent hair (pi. 19, fig. 200) arises a little to one side of 

 the principal tenent hair, but is shorter and weaker than the latter. 



