CarPENTER— Collembola from Franz-Josef Land. 275 
This species is nearly allied to Isotoma Reuteri, Schott (5), and 
I. sensibilis, Tullb. (7), which have two or three tenent hairs on 
the feet—an exceptional character in the genus Isotoma. J. 
brevicauda is readily to be distinguished from these by its propor- 
tionally shorter spring and smaller size, as well as by its peculi- 
arities of colour; the extension of the blue body-pigment into the 
proximal end of the dens, together with the pale terminal seg- 
ments of the antenne, gives it a very characteristic appearance. 
Fig. 12, Isotoma brevicauda, from side, x 27; fig. 13, antenna, post-antennal organ, 
and ocelli of left side, x 75; fig. 14, foot of first pair, x 180; fig. 15, foot of third 
pair, x 180; fig. 16, feathered bristles from tip of abdomen, x 200; figs. 17, 18, mucro 
from two specimens to show variation, x 180. 
In one specimen, however, the whole antenna is dark. The foot- 
claws, more especially those of the second and third pairs, are 
distinctly toothed. ‘This is a further character which, together 
with the four-toothed mucro, distinguishes the species from 
I. Reuteri; the latter, moreover, has the feathered bristles at the 
end of the abdomen longer, more robust, and clubbed. My best 
thanks are due to Dr. C. Schiffer for kindly sending me a 
specimen of 7. Reuteri for comparison, and enabling me to make 
