COLLEMBOLA OF THE FAMILY ISOTOMIDAE 41 



teeth. Unguiculus extending three-fifths as far as the unguis, broadly 

 lanceohxte, acute, un toothed, with a pair of inner lamellae. Tenent 

 hairs short; 2,2,2, or 3,3,3. Furcula appended apparently to the fifth 

 abdominal segment, short, extending only as far as the second abdom- 

 inal segment. Manubrium longer than dentes (as 5:4), stout, with 

 short curving dorsal setae, but naked ventrally. Dentes (pi. 13, 

 fig. 128) subcylindrical, narrowing but slightly, smooth dorsally, 

 without dorsal tubercles or folds, with short curving dorsal setae and 

 a few stiff ventral setae. Mucrones (pi. 13, fig. 128) almost one-half 

 as long as dentes, bidentate, with outer and inner lamellae well 

 developed, similar and equal; apical and anteapical teeth approxi- 

 mate, subequal, directed dorsally; ventral contour of mucro not 

 strongly rounded, in lateral aspect. Rami of tenaculum bidentate 

 (pi. 13, fig. 129); corpus with a single stout curving anterior seta. 

 Clothing (pi. 13, fig. 130) of minute curving equal setae, absent on 

 the intersegmental regions; erect sensory setae absent. Integument 

 smooth. Length, 1 mm. 



Cotypes.—U.S.'NM. no. 42981. 



Distribution. — Recorded as follows: 



Mississippi: Vicksburg, October 2, in decaying leaves and twigs, Dr. Henry E. 

 Ewing, for whom the species is named. 



PROISOTOMA (BALUSTURA) EXCAVATA, new species 



Plate 13, Figures 131-136; Plate 14, Figures 137, 138 



Description. — A stout, compact species. Pale yellowish (in alcohol) ; 

 body segments bordered posteriorly with narrow blackish bands; legs 

 pale; dentes pale; manubrium pigmented. Head large; oral region 

 strongly protuberant. A wide A-shaped marking extends forward 

 from the eye spots (pi. 13, fig. 131), and on each side of this marking 

 the head is excavate around the base of the antenna. Eyes (pi. 13, 

 fig. 132) six on each side, on black patches, the two inner proximal 

 eyes smaller than the others. Postantennal organ (pi. 13, fig. 132) 

 ovate to elliptical, one-fourth to one-half longer than the diameter of 

 the nearest eye. Antennae approximate, stout, with strongly tele- 

 scopic segments (pi. 13, fig. 133), in relative lengths about as 

 9:13:18:38; basal segment immersed in a pit and ringed basally with 

 pigment; second and third segments ringed apically; fourth pig- 

 mented throughout. Sense organ of third antennal segment (pi. 13, 

 fig. 134) close to distal end of segment, with a pair of slender linear 

 rods and two guard setae. Fourth antennal segment with slender 

 curving olfactory setae. Prothorax relatively small, concealed under 

 the head and mesonotum. Abdominal segments without ankylosis. 

 Fourth abdominal segment two and one half times as long as the 

 third. Tibiotarsus with a distal subs'egment (pi. 13, fig. 135). , Unguis 

 (pi. 13, fig. 135) stout, untoothed. Unguiculus extending three- 

 fourths as far as unguis, broadly lanceolate, setaceously prolonged 



