168 S. II Seudder— Diversity of Type in ancient Myriapods. 



shown by Ryder and Packard to differ from them in very 

 important features, in some at least of which it agrees with 

 Paheocampa. The researches of these naturalists, as well as 

 r 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 ThysaDura. 

 Ryder suggests for it an independent place between the Myri- 

 | Thyeanura under the name Symphyla. Packard, 

 with better reason, would place it within the Thysanura, under 

 which head he would also include the Collembola and Thy- 

 sanura proper, or Cinura, as he terms them. 



Scolopendrella, as these authors point out, differs from the 

 Chilopoda in that the appendages 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 segments, as legs, while the mouth parts resemble 

 those of Th from those of Chilopoda; indeed 



the whole head is decidedly thysanuriform ; the legs are pro- 

 vided 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 thysan- 

 uran, and the position <>l the stigmata, between the legs, ' J: 



from the position they uniformly maintain in Chilopoda, 

 1 adds to the great irregularity of place seen in 

 other hand, the identity of form 



its, the full development, upon 

 the abdominal segments, of jointed legs like those of the tho- 

 racic, segments, and the occasional alternation of leg 

 and apodal segments in the abdomen, are striking marks of its 

 real affinity to the chilopods. Abdominal appendages, homo- 

 logous with legs, but unjointed, do, however, occur in Thy- 

 sanura to a greater degree than in other hexapods, so that we 

 can hardly refuse to admit these polypodous creatures as low- 

 est 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 Paheo- 

 campa from the chilopods in the same way as it does Seolo- 

 pnidrella; so, too, the segments behind the head in Paheo- 

 eampa and Scolopendrella, alone of all arthropods in which the 

 head is thus clearly separated, agree in showing no distinction 

 whatever between what may be "looked upon as thoracic and 

 what as abdominal, whether in the iVn-m of the segment itself, 

 or in the appendages of the segments. These are certainly fun- 

 damental points, but when we have mentioned them we have 

 reached the end of all possible affinities, or points of resem- 

 blance, unless we may consider the minute structure of the 



