292 Mr. 8. H. Scudder on the Affinities of 
From this it will appear that Palceocampa differs in many 
essential features from Pertpatus, and in most at least of these 
shows a higher organization. ‘The segments are well sepa- 
rated from one another ; and the head is distinctly marked. The 
number of segments is much less; and each bears clusters of 
appendages of a highly specialized character. Although no 
spiracles are present in the remains we have of Palewocampa, 
it is clear that respiration must have been effected through 
linearly disposed openings, since the muscular or mechanical 
requirements for the movement of a completely segmented 
body (especially if, as in Paleocampa, the segments bear a 
heavy armature) forbid the miscellaneous distribution of tra- 
chee, and demand a well-developed system with the same 
linear arrangement which we find in the armature. The best 
that can be said of the respiratory apparatus in Peripatus is 
that the tracheal bundles show a tendency toward “ a con- 
centration along two sides of the body, ventral and lateral.” 
The possession, however, in each type, of a single pair of legs 
to every segment behind the head indicates an affinity which 
cannot be overlooked, and which is the more interesting since 
one of the types is very ancient and the other is universally 
looked upon as the existing survivor of an ancient type. The 
form of the body and of the fleshy legs is also similar; but 
there are minor points, and, however close the agreement be- 
tween these forms, we cannot look upon Paleocampa, with its 
undoubtedly well-developed tracheal development, as in any 
sense the genetic predecessor of Peripatus ; for the generally 
distributed tracheal apertures of the latter could not have de- 
veloped from a serial disposition without a degradation of 
type, which, as Moseley points out, many other features com- 
bine with this to disprove. It may also be added that while 
the legs of Paleocampa are poorly preserved in the only 
specimen which gives a side view, the presence of nephridial 
openings, of such an extent and in such a place as in Per?- 
patus, could hardly fail of detection, and they are entirely 
absent. The presence of these in Pertpatus is one of the 
marks of its inferior organization, or rather of its alliance to 
an inferior type, the annelids. 
The other aberrant group which we must specially notice is 
Scolopendrella, placed at first among Chilopoda, but recently 
shown by Ryder and Packard to differ from them in very 
important features, in some at least of which it agrees with 
Paleocampa. 'The researches of these naturalists, as well as 
the earlier observations of Menge, clearly prove that it must 
be separated from the myriopods altogether, and that it is 
certainly provided with many points of affinity to the Thy- 
