290 > s - H. SCUDDER OX NEW TYPES 



known, whether living or fossil, we are brought face to face with two remarkable and 

 somewhat parallel facts: First, that in this ancient myriapod, as old as any with which we 

 are acquainted, carrying us back indeed as far as any traces of wingless tracheate arthro- 

 pods have been found, and, therefore, presumably not far from the origin of this form of 

 life upon the earth, toe find dermal appendages of an extraordinarily //it/It organization, 

 more complicated, as we have pointed out, than anything of the sort found in living arthro- 

 pods, excepting the more varied but not more exquisite scales of several orders of hexa- 

 pods ; a form of appendage which it would seem, on an}- genetic theory of development, 

 must have required a vast time to produce, but which we now seem to find at the very 

 threshold of the apparition of this type of arthropod life. 



Second, that at this early period, in marked contrast to what we find in other groups of 

 avticulated animals, the divergencies of structure among myriapods was as great as it is 

 to-day. This is the more surprising because we possess only imperfect remains of a few 

 types, and yet from what we already know of the Archipolyp >da on the one hand, and of 

 the Protosyngnatha on the other, they are found to differ quite as much as the Diplopoda 

 and Chilopoda, and in points fully as important as those which separate so sharply these 

 great modern groups. Whether they are to be looked upon, one as the ancestor of one, 

 the other of the other, of these modern groups, is another question. It would certainly 

 be reasonable to consider the Archipolypoda as the common ancestors of both the Chilo- 

 poda and Diplopoda ; and possibly on the Protosjmgnatha as the descendants on one line 

 of a primitive type which, on another line, has retained its integrity up to the present day 

 in Peripatus (and on possibly a third line has reached Scolopendrella) ; while on that which 

 produced Palaeocampa it has not, so far as we know, survived the carboniferous epoch. 



With the facts of structure of ancient and modern types now before us, we are compelled, 

 on any genetic theory, either to presume a great acceleration of development in earlier 

 times or to look for the first appearance of myriapods at a vastly remoter epoch than we 

 have any reason to do from the slight hints in the rocks themselves — a period so remote 

 as to antedate that of winged insects, which are now known from rocks older than any 

 which have yielded remains of myriapods. 1 In a memoir on Devonian insects, 2 I showed 

 the probabilitjr, on developmental grounds, that some of the carboniferous insects, •• to- 

 gether with most of those of the Devonian, descended from a common stock in the lower 

 Devonian or Silurian period; and that the union of these with the Palaeodictyoptera (of 

 the carboniferous), was even further removed from us in time." The structural relations 

 of myriapods and hexapods render it probable that the former preceded the latter ; and 

 in complete accordance with this expectation, the structural relations of the oldest fossil 

 myriapods indicate their apparition at a period earlier than that to which the winged 

 insects are hypothetically assigned. This would compel us to consider the earlier type as 

 aquatic, for which we have presumptive evidence in the structure of the Euphoberidae, 

 and renders it all the more surprising that the penetrating researches of the last thirty- 

 seven years, since the first carboniferous myriapod was discovered, have not yielded the 

 slightest trace of fossil myriapods below the Coal measures. 1 This discrepancy between 

 fact and hypothesis should never be lost sight of, and should stimulate to more searching 



1 This was written before the publication of Mr. Peach's discov- 2 Anniv. Memoirs Bust. Sue. Nat. Hist., 1880. 

 ery of myriapods in the OH lied Sandstone of Scotland. 



