288 S. H. SCUDDER OX NEW TYPES 



one another, and scattered over the body, and the longitudinal muscles show no regular 

 segmental breaks. This weakness of segmental divisions is nowhere paralleled among 

 hexapods, arachnids or myriapods, and is an indication of very low organization among 

 arthropods generally. The number of legs indicates from 15 to 35 segments in the 

 body, according to the* species. The first pair, as they are developed in the adult, are func- 

 tionless as legs, and are situated (in the specimens I have examined — a South American 

 species, probably P. Edwardsii), midway between the antennae and second pair of leu-. 

 and not only outside of, but at some distance from the mouth part>, so that the latter are 

 not furnished 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 regular distribution. 



From this it will appear that Palaeocampa differs in many essential features from Peri- 

 patus, 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 appendages of a highly specialized character. Al- 

 though no spiracles are present in the remains we have of Palaeocampa, it is clear that res- 

 piration 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 Palaeocampa, the segments bear a heavy armature), forbid the miscellaneous dis- 

 tribution of tracheae, and demand a well-developed system with the same linear arrange- 

 ment which we find in the armature. The best that can be said of the respiratory appara- 

 tus in Peripatus is that the tracheal bundles show a tendency toward "a concentration 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 he 

 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 fleshy l?gs 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. It 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 shown by Ryder and Packard to differ from them in 

 very important features, in some at least of which it agrees with Palaeocampa. The 

 researches of these naturalists, as well as the earlier observations of Menge, clearly prove 

 that it must be separated from the myriapods altogether, and that it is certainly provided 

 with many points of affinity to the Thysanura. Ryder suggests for it an independent 

 place between the Myriapoda and Thysanura under the name Symphyla. Packard, with 



