COLLEMBOLA OF THE FAMILY ISOTOMIDAE 55 



This species comes close to Isotoma minima Absolon (1900a, 1900b, 

 1901), in which, however, the eyes are isolated on separate pigment 

 spots, the third abdominal segment is almost as long as the fourth, 

 and the third tooth of the mucro is close to the second. 



Proisotoma sepulcralis is a species of the soil. Though the speci- 

 mens that I examined in preparing the original description numbered 

 more than 5,400, they are the only examples of the species that I 

 have ever seen. They were collected from graves in Washington, 

 D. C, during the summers of 1896 and 1897, by Dr. Murray Gait 

 Hotter. 



Cotypes.—\J.S.l<iM. no. 6144. 



PROISOTOMA (PROISOTOMA) FRISONI. new species 



Plate 20, Figures 216-219; Plate 21, Figures 220-222 



Description. — Wliite. Eyes absent. Postantennal organ (pi. 20, 

 figs. 216, 217) elliptical, with a thick wall, in length one-half the basal 

 mdth of the first antennal segment. Antenna! base strongly de- 

 veloped (pi. 20, fig. 216), about one-half as long as the first antennal 

 segment. Antennae longer than the head (as 9:8), with segments in 

 relative lengths about as 4 : 7 : 6 : 1 3 . First segment cjdindrical, second 

 and third subclavate, fourth elUptical. Sense organ of third antennal 

 segment (pi. 20, fig. 218) with a pair of slender, rather long rods, a 

 chitinous ridge and two setae. Fourth antennal segment without 

 special olfactory setae. Abdominal segments without ankylosis. 

 Fourth abdominal segment longer than the tliird (as 6:5). Unguis 

 (pi. 20, fig. 219) without lateral or inner teeth. Unguiculus extending 

 two-thirds as far as the unguis on the hind feet; one-half as far on the 

 fore feet. Tenent hairs 1, 1, 1. Furcula short, extending only to the 

 posterior part of the second abdominal segment. Manubrium (pi. 21, 

 fig. 220) longer than dentes (as 5:3), with four pairs of ventral sub- 

 apical stout setae. Dens stout (pi. 20, fig. 220), but narrowing gradu- 

 ally, with six short stiff ventral setae; dorsally with about 10 or 12 

 small, somewhat irregular intermediate crenulations. Mucro (pi. 21, 

 figs. 221, 222) elongate, one-third or two-fifths as long as dens, tri- 

 dentate; apical tooth almost straight or shghtly curving; anteapical 

 about as long as apical, but stouter, erect or shghtly inchned; third 

 tooth the smallest, as a rule (though sometimes subequal to second), 

 proximal, lateral, obhque. Rami of tenaculum quadridentate; 

 corpus with three stout curving anterior setae. Clothing of dense 

 minute stiff reclinate setae; erect sensory setae absent. Integument 

 smooth. Maximum length, 1.1 mm. 



Cotypes.— V.S.N. M. no. 42978. 



Distribution. — Recorded as follows: 

 Illinois: Cahokia, May 8, T. H. Frison (Illinois State Natural History Survey). 



