If,-}- >. //. Srinhh-r — Diversity of Type in anri, ,,t J/y/vVyW.v. 



The differences between the stout, forked and bristling spines 

 of the Archipolypoda and the close set but spreading bunches 

 of highly organized stiff rods of Palaeocampa appear upon the 

 tement. Were it not however for the complicated 

 ornamentation of the rods themselves, the distinction between 

 the fascicles of Palaeocampa and the spines of Euphoberia would 

 be hardly greater than that between the latter and the long 

 hairs of an undescribed genus of Archipolypoda which has re- 

 cently fallen under notice ; so that to this feature alone we can- 

 not grant so high an importance as to another which has already 

 been named : the presence in Palceocampa of a single pair of 

 legs (and consequently, to judge by analogy, of a single ven- 

 tral plate) to each segment; while there are two ventral plates 

 and pairs of legs to each segment in Archipolypoda. This is a 

 difference of profound significance, which has separated the 

 g types of myriapods down to the present" day, lying 

 as it does at the base of the distinctions between th 

 chilopods and diplopods. . The discovery of this type is of the 

 greater importance because we have hitherto known nothing of 

 any chilopodiform myriapods previous to Tertiary times, unless 

 Minister's dubious GeojJidus proavus from the Jura possibly be 

 an exception. 



In studying the Archipolypoda we necessarily confined our 

 comparisons with modern types to the Diplopoda, because of 

 sion of the fundamental feature just 

 way the comparisons between Palaso- 

 campa aim recent iorms must be reduced to the common fea- 

 tures or the radical distinctions which appear in studying the 

 Chilopoda. Now although the structure of Palaeocampa can 

 be far less perfectly known than that of the equally ancient 

 Euphoberia and its allies, enough can be seen to point con- 

 clusively to wide and important differences between it and 

 modern Chilopoda. 



In Chilopoda, of which the modern scolopendra or centipede 

 is the type, the body is always depressed, formed of many 

 segments, rarely as few as sixteen behind the head, each of which 

 is compound, being formed of two subsegments, one of them 

 atrophied and carrying no appendages ; both dorsal and ven- 

 tral plates are coriaceous, of nearly equal width, and possess 

 no armature whatever excepting the simplest hairs, which are 

 occasionally scattered over the surface. The larger subsegment 

 bears a single pair of legs, which are composed of five slender, 

 cylindrical, subequal joints beyond the coxa, and armed with a 

 single apical claw ; they are attached to the interscutal mem- 

 brane uniting the distinct dorsal and ventral plates of each 

 segment and are therefore separated by the entire width of the 

 broad ventral plates. The hindmost • legs are transformed to- 



