VERTICAL RANGE OF THE ARACHNIDA 681 
TABLE SHOWING THE VERTICAL RANGE OF THE ARACHNIDA.! 



| Z | 
Orders. = | 3 cae [ey 2 | 3 | 3 Z + 
ala|sljea ls aa Z 8 
ACARI . | 
CHELONETHI 
ANTHRACOMARTI . 
PEDIPALPI 
SCORPIONES . 
OPILIONES 
ARANEAE 










SuB-PHyLuM B. MyRIopopDa. 
Tracheate Arthropods with distinctly separated head and numerous fairly similar 
segments, each of which bears one or two pairs of legs. Body vermicular, apterous. 
Head with one pair of antennae and three patrs of jaws. 
The head in Myriopods is formed by a single division, which only in exceptional 
cases is supplemented by parts of the following body segments. The two most 
important orders are Chilopoda and Diplopoda. In the former, which approaches very 
closely to Insects, every body segment possesses a single dorsal and a ventral plate, to 
which a pair of legs is attached. The 
Diplopods, on the other hand, show on every 
segment except the first a dorsal plate and 
two ventral plates, with two pairs of legs. 
A precursor of the Chilopods is found 
in the genus Palaeocampa, M. and W., trom 
the Carboniferous, whose body 18 composed Archidesmus Macnicoli, Peach. Devonian; For- 
of but a few segments. Scudder places it farshire, Scotland. 1/ (after Peach). 
in a distinct order, Protosyngnatha. True 
Chilopod genera (Cermatia, Rossi; Scolopendra, Linn.; Lithobius, Geophilus, Leach) 
occur in amber and the fresh-water gypsum of 
Aix, Provence. 
Most Palaeozoic Myriopods are of large size 
and belong to the order Archipolypoda, in which 
all body segments possess two dorsal and two 
ventral plates, with two pairs of legs. Two 
genera are found in the Old Red Sandstone of 
Scotland, Archidesmus, Peach (Fig. 1438); and 
Kampecaris, Page. Numerous others occur in 
the Carboniferous and Trias of both continents, 
Euphoberia armigera, Meek and W. Coal = 5 
Measures ; Mazon Creek, Illinois, 1/3, and some have been recognised by Matthew in 
the Devonian of New Brunswick. Fxamples: 
Euphoberia, M. and W. (Fig. 1439); Amynilispes, Scudder; Xylobius, Dawson ; 
Acantherpestes, M. and W., a genus regarded by Scudder as probably amphibious. 
From Mesozoic rocks but a single species is known (Julopsis cretacea, Heer). 

Fic. 1438. 

Fic. 14389. 
1 The figures indicate the number of species, as estimated in 1885. 
