OF CARBONIFEROUS MYRIAPODS. 289 



better reason, would place it within the Thysanura, under which head he would also include 

 the Collembola and Thysanura proper, or Cinura, as he terms them. 



Seolopendrella, as these authors point out, differs from the Chilopoda in that the appen- 

 dages of the segment behind that furnishing the mouth-parts proper do not serve as 

 auxiliary organs for manducation, but are developed, like those of the succeeding seg- 

 ments, as legs, while the mouth parts resemble those of Thysanura. and differ from those 

 of Chilopoda ; indeed the whole head is decidedly thysanuriform ; the legs are provided 

 with a pair of claws, and the terminal segment bears a pair of caudal stylets with a special 

 function. Besides these points the possession of a collophore is distinctively thysanuran, 

 and the position of the stigmata, between the legs, is different from the position they 

 uniformly maintain in Chilopoda, while it only adds to the great irregularity of place seen 

 in Thysanura. On the other hand, the identity of form in the thoracic and abdominal 

 segments, the full development, upon the abdominal segments, of jointed legs like those 

 of the thoracic segments, and the occasional alternation ot leg-bearing and apodal segments 

 in the abdomen, are striking marks of its real affinity to the chilopods. Abdominal appen- 

 dages, homologous with legs, but unjointed, do, however, occur in Thysanura to a greater 

 degree than in other hexapods, so that we can hardly refuse to admit these polypodous 

 creatures as lowest members of the sub-class of insects proper, although they are the only 

 non-hexapodal type. 



Now the separation of the head and its appendages from those of the next succeeding 

 segment distinguishes Palaeocampa from the chilopods in the same way as it does Seolo- 

 pendrella; so, too, the segments behind the head in Palaeocampa and Seolopendrella, alone 

 of all arthropods in which the head is thus clear!}' separated, agree in showing no distinc- 

 tion whatever between what may be looked upon as thoracic and what as abdominal, 

 whether in the form of the segment itself, or in the appendages of the segments. These 

 are certainly fundamental points, but when we have mentioned them we have reached the 

 end of all possihle affinities, or points of resemblance, unless we ma)' consider the minute 

 structure of the rods in the fascicles of Palaeocampa parallelled by the well-known delicacy 

 of organization of the scales in some Thysanura, though they do not exist in Seolopen- 

 drella. The limited number of abdominal segments might be looked upon as a further 

 point were it not that the number is even less than in Seolopendrella or in the Cinura; 

 and that the Pauropida among diplopod myriapods 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 forms so 

 striking a feature in Palaeocampa, the want of any caudal stylets, and the complete uniform- 

 ity of the segments of the body unprovided with distinct dorsal scutes, distinguish Palaeo- 

 campa not only from Seolopendrella but from all Thysanura whatever; the general form 

 of the body, too, is altogether different from anything 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 affinity between Palaeocampa and Seolopendrella, 

 with the single exception of the separation of the head and its appendages from the body, 

 are precisely those in which Seolopendrella is chilopodan, and that the assemblage of fea- 

 tures which our fossil presents are therefore chilopodan rather than thysanuran. 



Regarding Palaeocampa then as a myriapod, though of a type very distinct from any 



