116 BULLETIN 168, UNITED STATES NATIONAL MUSEUM 



hairs absent; in their place, a strong simple seta. Furcula attaining 

 the ventral tube. Manubrium short and stout, with a few stiff setae 

 dorsally and ventrally. Dentes almost three times as long as the 

 manubrium (as 11:4), slender and tapering, dorsally multicrenu- 

 late, ventrally with many stiff setae and a strong subapical seta 

 extending almost to the end of the mucro. Mucrones (pi. 38, figs. 

 445-448) shorter than hind unguicuU, tridentate. The teeth of the 

 mucro are quite variable in form and size. Apical tooth slender to 

 stout, acute to obtuse, directed dorsally or subdorsally; anteapical 

 tooth stout, erect; third tooth lateral, large or small. Kami of tenac- 

 ulum quadridentate. General clothing (pi. 38, fig. 449) of curving 

 simple setae, moderately long; outstanding sensory setae strong, 

 unilaterally fringed. Length, 1.9 mm. 



In a partly grown individual, 1.4 mm in length, the body segments 

 are bordered with dark violet and have a fine median dorsal Une. 

 Front with a transverse mark connecting the eye spots and antennal 

 bases. Occiput with a A-shaped mark connecting the eye spots. 

 Antennae one and one-half times as long as the head, with segments 

 as 6 : 8 : 10 : 15. Third and fourth abdominal segments equal in length. 

 Corpus of tenaculum with five setae: a strong median seta and two 

 pairs of small setae. 



Remarks. — Plate 38, figures 445 to 448, inclusive, are all from the 

 same individual. The latter was about to molt, and the new mu- 

 crones (pi. 38, figs. 446, 448) could be seen inside the dentes. 



This species closely resembles viridis, from which it differs chiefly 

 as regards mucrones, eyes, and postantennal organs. 



Cotypes.—V.S.'N.M. no. 42971. 



Distribution. — Recorded as follows: 



Washington: Friday Harbor, June 27, on moss-covered rocks, M. W. Shackle- 

 ford. 

 Canada: Arnprior, Ontario, October, C Macnamara. 



UNIDENTIFIED SPECIES 



ISOTOMA GLAUCA Packard 



Plate 39, Figure 450 



Isotoma glauca Packard, 1873, p. 33.— MacGillivray, 1891, p. 273.— von Dalla 

 Torre, 1895, p. 10. 

 Description. — Packard's original description of this species is as 

 follows: 



Isotoma glauca, n. sp. A bluish gray species, very slender, intermediate in 

 form between /. albella and the stouter species, /. tricolor, etc. Head shorter 

 than in I. albella, eye patches black, conspicuous, broader, less linear than in 

 I. albella. Antennae much shorter and stouter than in I. albella, basal joint one- 

 half shorter than in that species, second and third joints much more dilated 

 distally. Body a little more hairy than in /. albella; spring of much the same size 

 and proportions; the lower edge finely serrulate, with rounded teeth, and the 



