8. H. Scudder — Diversity of Type in ancient Myriapods. 167 



species, probably P. Edwardsii), midway between the antennae 

 and secoud pair of legs, and not only outside of but at some 

 distance from the mouth parts, so that the latter are not fur- 

 nished with auxiliary appendages borrowed from a segment 

 behind the first, as in chilopods; this is further proven by the 

 development of these parts in the two groups. The body is 

 profusely covered above with corrugated papillae, without reg- 

 ular distribution. 



From this it will appear that Palaeocampa differs in many 

 essential features from Peripatus, and in most at least of these 

 shows a higher organization. The segments are well separated 

 from one another, and the head is distinctly marked. The 

 number of segments is much less, and each bears clusters of 

 ges of a highly specialized character. Although no 

 spiracles are present in the remains we have of Palaeocampa, it 

 is clear that respiration must have been effected through lin- 

 early disposed openings; since the muscular or mechanical 

 requirements for the movement of a completely segmented 

 body (especially if, as in Palaeocampa, the segments bear a 

 heavy armature), forbid the miscellaneous distribution of tra- 

 cheae, and demand a well-developed system with the same lin- 

 ear 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 concentration 

 along two sides of the body, ventral and lateral." The posses- 

 sion, 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 an existing survivor of an ancient type. The form of the 

 body and of the flesh v legs is also similar, but these are minor 

 points: and however close the agreement between these forms 

 we cannot look upon Palaeocampa, 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 developed from a serial 

 disposition, without a degradation of type which, as Moseley 

 points out, many other features combine with this to disprove. 

 ft may also be 'added that while the legs of Palaeocampa 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 Peripatus, could hardly fail of detection, and 

 they are entirely absent. The presence of these in Peripatus 

 is one of the marks of their inferior organization, or rather of 

 their 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 



