286 GEOGRAPHICAL AKD GEOLOGICAL DISTRIBUTION. 



forms, and representing spiders (Protolycosa, Architarbus, Anthra^ 

 comartus), scorpions (Cyclopthalmus, Eoscorpius), and pseudo-scor- 

 pions (Microlabis), are met with. In the Mesozoic deposits but few 

 arachnoid remains, in rnost cases in an imperfect st^ite of preserva- 

 tion, have thus far been discovered, and it is not until about the 

 middle of the Tertiary series, Oligoceue, that they acquire by their 

 numbers any imjDortance. The amber deposits of Europe and the 

 Florissant beds of Colorado have yielded' the greatest abundance 

 of such remains. 



It is not a little remarkable with what degree of persistence 

 the fundamental characters of scorpions have been preserved, for 

 it appears, as has been claimed by Mr. Peach, that the Car- 

 boniferous forms, as represented by Eoscorpius, were as highly or- 

 ganised and specialised towards the beginning of this period as 

 their descendants of the present day. The Paleozoic araneids, on 

 the other hand, appear to have been all, or in the main, possessed 

 of distinctly segmented abdomens, thereby forming a transitionary 

 group between the arthrogastric and non-arthrogastrio arachnoids. 



Both the chilognathous and chilopodous types of Myriapoda may 

 be said to be represented in the Carboniferous rocks, although from 

 certain peculiarities of structure possessed by these early forms — 

 the genera Euphoberia, Xylobius, Acantherpestes, Trichiulus, among 

 the former, and Palseocampa among the latter — which are un- 

 known in their modem representatives, special ordinal groups, the 

 Archipolypoda and Protosyngnatha respectively, have been created 

 for them. It may be doubted, however, whether such knowledge 

 as we possess of the animals in question will pemiit of the reten- 

 tion of these groups ; indeed, it appears by no means certain that 

 all the forms referred here as Myi-iapoda are actually such at all. 



The earliest myriapod remains, referred by Peach "' to the Chilo- 

 gnatha, occur in the Old Red Sandstone (Devonian) of Forfarshire, 

 Scotland, and not improbably the problematical Gyrichnites of the 

 nearly equivalent deposit of 6asp6 are the belongings of these 

 animals. The Mesozoic rocks are singularly deficient in their traces, 

 and may be said to be almost wholly wanting in them ; excepting 

 the somewhat doubtful Geophilus proavus from the Jurassic deposits 

 it appears that no chilopodous form is met with before the Ter- 

 tiary. 



