TRACHEATA 319 
but five, each of which in the last-named genus bears two 
pairs of legs. The last segment of the antenna of Pauwropus 
bifurcates and bears three flagella (Fig. 183). 
Scolopendrella, the genus which constitutes the sub-order 
Symphyla, has obvious resemblances to certain members of 
the most primitive sub-order of the Insecta, the Thysanura, 
and in spite of the fact that no clear division of thorax and 
Fia. 184.—Scolopendrella immaculata, 
highly magnified. Slightly altered 
from Packard. 
a. Caudal stylets. 
b, 6. First postcephalic appendages. 
c. Antennae. 
2. One of the functional legs further 
enlarged (from Wood Mason), 
showing the five joints and 
terminal pair of claws, 
6, Inner rudimentary leg of same 
somite. 
abdomen exists, and that practically all the segments bear 
legs, and there are only two pairs of mouth appendages, it 
has been proposed to class this animal with the Thysanura. 
Scolopendrella is but 5 or 6 mm. long; behind the head there 
are fifteen terga, but only thirteen sterna exist, and twelve 
pairs of legs; the latter are five-jointed and terminate in two 
claws (Fig. 184), as in Campodea, the genus of Thysanura it 
most closely resembles. At their base is a small process 
which gives the limb almost a biramous character, <A pair 
of caudal styles bear the apertures of certain silk glands. 
