& H. Scudder — Diversity of Type in ancient Myriapods. 163 



appendages of such delicate and specialized organization occur 

 anywhere to-daj among arthropods, unless it be when devel- 

 oped as scales, as in Lepidoptera, and occasionally in other 

 groups of hexapods ; some ehsetopod worms have indeed hairs of 

 curious asymmetrical structure, often very delicate and some- 

 ulized, but never, so far as lean learn, to nearly so 

 high a degree as here. The collection of these rods into fascicles 

 is also not a little curious, and is again a feature known now 

 in arthropods only in a few instances, such as some tufts of 

 hairs in lepidopterous caterpillars like Orgyia ; or the pencils of 

 hair-like scales in the males of some perfect Lepidoptera, e. g. 

 at the tip of the abdomen in Heliconia, Da ris, A-rotis, Leu- 

 carctia, etc. ; or in the terminal fascicles of barbed hairs in the 

 myriapodan genus Polyxenus. 



There is no group of animals into which such a jointed crea- 

 ture as this could fall excepting worms, myriapods, or the lar- 

 vae of hexapod insects. The certainty that this animal pos- 

 sessed a single pair of well developed, legs of identical charac- 



tthe 



worms and from the larvae of hexapod insects. No such legs 

 or leg-like structures occur to-day in worms, and it would be 

 idle to look for them in their ancestors of Carboniferous times. 

 The only approach to such an appearance in hexapod larvae is 

 in the young of tenthredinous Hymenoptera, where, however, 

 a difference of great morphological significance is found be- 

 tween the true or thoracic legs and the prolegs or those at- 

 tached to the abdomen ; a difference based on one of the most 

 essential underlying features of their structure as hexapods. 

 No such difference occurs in Palaeocampa, and it is therefore 

 impossible to conceive of it as the larva of a hexapod insect of 



In myriapods only do we find a repetition of legs of exactly 

 similar structure on every or nearly every segment of the 

 body;* by this test Palaeocampa is a myriapod ; and now that 

 we 'have "found ancient types of this group, like the Arcbi- 

 polypoda, bearing huge and bristling spines arranged in series 

 along the sides of the body, we need not be at all disconcerted 

 •. tvpe. with longitudinal series of fasci- 

 cles of stiff rods, althou.u i we cannot restrain our surprise and 

 a! tiuir exquisite intricate structure. 



Accepting Pahrocampa then as a myriapod. we may next 

 ask what relation it bore to the myriapods of the same period 

 and found in the same waters, and also to myriapods of to-day. 



