16 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



FOLSOMIDES STACHI, new species 



Plate 2, Figures 21-23; Plate 3, Figures 24-26 



Description. — White. Greatly elongate; body cylindrical, in length 

 six times the height of the abdomen. Eyes (pi. 2, fig. 21) one on 

 each side, each on a small round black spot. Postantennal organ 

 (pi. 2, fig. 21) close to the eye, narrowly elliptical, straight or feebly 

 curving, in length about four times the diameter of the eye, with four 

 guard setae. Antennae about two-thirds as long as the head, with 

 segments in relative lengths about as 5:6:7:8. Body segments in 

 relative lengths about as 14:27:25:21:23:24:27:20:15. Fourth ab- 

 dominal segment thus a httle longer than the third. Genital and 

 anal segments not ankylosed. Anus caudal. Unguis (pi. 2, figs. 

 22, 23) stout, curving, untoothed. Unguiculus extending one-half 

 as far as unguis on hind feet, one-third as far on the remaining feet, 

 lanceolate, acuminate, untoothed. Tibiotarsus with a distal sub- 

 segment indicated. Tenent hairs absent. Furcula small, appended 

 to the posterior part of the fourth abdominal segment, and extending 

 not quite to the middle of the third. Manubrium (pi. 3, figs. 24, 25) 

 longer than mucrodens (about as 3:2), gradually narrowing, with five 

 pairs of setae in dorsal aspect (pi. 2, fig. 25). Dens and mucro 

 confluent. Mucrodens (pi. 2, figs. 24, 25) stout, gradually tapering 

 from the base, with three small dorsal setae; mesally with a pair of 

 narrow chitinous basal ridges. Mucro minutely bidentate (pi. 2, 

 fig. 26) ; apical tooth hooked ; anteapical retrorse. Rami of tenaculum 

 tridentate; corpus with an anterior median basal lobe. Clothing of 

 minute, stiff, simple setae, limited to a few transverse rows across the 

 middle of each body segment, with a few longer erect sensory setae; 

 genital and anal segments with a few long setae. Integument smooth. 

 Length, 0.6 mm. 



Remarks. — This new species, which is dedicated with pleasure to 

 my colleague Dr. Jan Stach, was taken by me at Tallulah, La., 

 April 7, in humus in a cypress forest. 



(7of?/pgs.— U.S.N.M. no. 42992. 



Genus ISOTOMODES Linnaniemi 



Isotoma Axelson, 1903a, p. 6; 1906, p. 11. 



Isotomodes Linnaniemi (Axelson), 1907, p. 34; 1912, p. 106. — Shoebotham, 

 1911, p. 34.— Handschin," 1925b, p. 164. 



Genotype. — Isotomodes productus Linnaniemi. 



Body greatly elongate. Prothorax unusually long. Genital and 

 anal segments shortened and not distinctly separated from each other. 

 Anus ventral. Integument granulate. Clothing of simple setae. 

 Antennae 4-segmented, arising relatively far forward. Head narrow 

 and low. Mouth parts mandibulate, projecting a little. Sense organ 

 of third antennal segment present, consisting of two sense rods, each 



