294 Mr. S. H. Scudder on the Affinities of 
in Scolopendrella or in the Cinura, and that the Pauropida 
among diplopod myriopods have in some instances even a still 
smaller number. On the other hand, the character of the 
legs, the apparent absence of a double claw at their tip, the 
peculiar armature of the fascicled rods, which form so striking 
a feature in Paleocampa, the want of any caudal stylets, and 
the complete uniformity of the segments of the body unpre- 
vided with distinct dorsal scutes distinguish Paleocampa not 
only from Scolopendrella, but from all Thysanura whatever ; 
the general form of the body, too, is altogether different from 
any thing occurring there, even its cylindricity being foreign 
to the Thysanura, excepting in their highest types among the 
Collembola. It seems therefore clear that the points of affi- 
nity between Paleocampa and Scolopendrella, with the single 
exception of the separation of the head and its appendages 
from the body, are precisely those in which Scolopendrella 
is chilopodan, and that the assemblage of features which our 
fossil presents are therefore chilopodan rather than thy- 
sanuran. 
Regarding Paleocampa, then, as a myriopod, though of a 
type very distinct from any known, whether living or fossil, 
we are brought face to face with two remarkable and some- 
what parallel facts :—First, that in this ancient myrtopod, as 
old as any with which we are acquainted, carrying us back 
indeed as far as any traces of wingless tracheate arthropods 
have been found, and therefore presumably not far from the 
origin of this form of life upon the earth, we find dermal ap- 
pendages of an extraordinarily high organization, more compli- 
cated, as we have pointed out, than any thing of the sort found 
in living arthropods, excepting the more varied but not more 
exquisite scales of several orders of hexapods—a form of ap- 
pendage which it would seem, on any genetic theory of de- 
velopment, must have required a vast time to produce, but 
which we now seem to find at the very threshold of the appa- 
rition of this type of arthropod life. 
Second, that at this early period, in marked contrast to what 
we find in other groups otf articulated animals, the divergences 
of structure among myriopods was as great as i is today. 
This is the more surprising because we possess only imperfect 
remains of a few types; and yet from what we already know 
of the Archipolypoda, on the one hand, and of the Protosyn- 
gnatha on the other, they are found to differ quite as much as 
the Diplopoda and Chilopoda, and in points fully as important 
as those which separate so sharply these great modern groups. 
Whether they are to be looked upon, one as the ancestor of 
one, the other of the other, of these modern groups, is another 
