94 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



16:18). Unguis and unguiculus without teeth. Tenant hairs absent. 

 Furcula appended to the fifth abdominal segment, attaining the 

 ventral tube. Dentes twice as long as manubrium. Mucro (pi. 30, 

 fig. 345) tridentate. Dens with a long subapical seta extending 

 almost as far as the apex of the mucro. Length, 0.6 mm to 0.8 mm. 



Remarks. — Scherbakov found this species abundantly under 

 flowerpots and in boggy soil in southwestern Russia. Wahlgren 

 recorded it from moss in eastern Greenland, and remarked that it is 

 easily overlooked on account of its minute size. 



The preceding description and the figure are from Scherbakov. 



ISOTOMA asOTOMA) MINOR Schaffer 



Plate 30, Figures 346-352 



Isotoma minor Schaffer, 1896, p. 182. — Scherbakov, 1898a, p. 59; 1898b' 

 p. 10.— AXELSON, 1900, p. 113; 1904, p. 71; 1905b, p. 34; 1906, p. 13.— Borner, 

 1901a, p. 53.— Agren, 1903, p. 138.— Becker, 1902, p. 28.— Krausbauer, 

 1902, p. 43.— ScHOTT, 1902, p. 23.— Philiptschenko, 1905, p. 3.— Wahl- 

 gren, 1906a, p. 225; 1906b, p. 256; 1919, p. 751. — Linnaniemi (Axelson), 

 1907, p. 21; 1909, p. 9; 1911, p. 19; 1912, p. 172.— Collinge and Shoe- 

 BOTHAM, 1909, p. 88; 1910, p. 107.— Brown, 1919, p. 64; 1923, p. 262.— 

 Stack, 1921, p. 163; 1922a, p. 23.— Denis, 1924a, p. 260.— Handschin, 

 1924a, p. 113; 1924b, p. 85; 1928a, p. 542; 1929, p. 65.— Womersley, 

 1925, p. 219; 1927, p. 376. 



Description. — White. A slender species. Eyes absent. Postan- 

 tennal organs absent. Antennae longer than the head, with stout 

 segments, in relative lengths about as 16:21:23:41. Sense organ of 

 third antennal segment (pi. 30, fig. 346) with a pair of slender straight 

 rods lying free, that is, not in a groove. Fourth antennal segment 

 with five to eight (commonly six) distal, lateroventral, relatively 

 large sensory cones (pi. 30, fig. 347). In addition to these there are 

 several "olfactory" setae of the usual type. In dorsal aspect, six 

 outer and three inner setae of this type may be seen. Unguis (pi. 30, 

 fig. 348) stout, without lateral or inner teeth. Unguiculus broadly 

 lanceolate, acute, untoothed, extending more than half as far as the 

 unguis on the hind feet, and half as far or less on the remaining feet. 

 Tenent hairs absent. Fourth abdominal segment a little longer than 

 the third (as 37:33). Genital and anal segments ankylosed. Furcula 

 appended to the fifth abdominal segment, extending not quite to 

 the ventral tube, slender and tapering. Dentes slender, gradually 

 tapering, two and one-half to three times as long as the manubrium, 

 dorsally crenidate except on the distal third, with short stiff ventral 

 setae. Mucrones minute, tridentate (pi. 30, figs. 349-351). Apical 

 tooth relatively long, hooked; second smaller, in line with the first 

 tooth, suberect; third tooth lateral, opposite the second, oblique. 

 Dens with a strong subapical seta exceeding the mucro. Rami of 

 tenaculum quadridentate; corpus with one ventral seta. General 

 clothing of short simple setae. Long, stout, more or less curving, 



