144 HISTORICAL PALZONTOLOGY. 
in many specific forms (figs. 86 and 87); but almost all the 
known examples are of small size, and are liable to escape a 
@. ; 
&§ WY 
TNS 
Fig. 87.—a, Spivorbis omphalodes, natural size 
and enlarged, Devonian, Europe and America ; 
6, Spirerbis Arkonensis, of the natural size and 
enlarged ; c, The same, with the tube twisted in 
the reverse direction. Devonian, America. (Ori- 
ginal.) 
_Fig. 88.—a 4, Spirorbis laxus, enlarged, Upper 
Silurian, America; c, Spivorbis spinulifera, of the 
natural size and enlarged, Devonian, Canada. (Af- 
ter Hall and the Author.) 
cursory examination. 
The Crustaceans of 
the Devonian are prin- 
cipally Zurypterids and 
Trilobites. Some of the 
former attain gigantic 
dimensions, and the 
quarrymen intheScotch 
Old Red give them the 
name of “ seraphim,” 
from their singular 
scale-like ornamenta- 
tion. The Z7zlobites, 
though still sufficiently 
abundant in some local- 
ities, have undergone a 
yet further diminution 
since the close of the 
Upper Silurian. In both 
America and Europe 
quite a number of gen- 
eric types have survived from the Silurian, but few or no new 
ones make their appearance during this period in either the Old 
Fig. 88.—Devonian Trilobites a, Phacops latifrons, Devonian of Britain, the Conti- 
nent of Europe, and South America; 6, Homalonotus armatus, Europe; c, Phacops 
(Trimerocephalus) levis, Europe; a, Head-shield of Phacops (Portlockia) granulatus, 
Europe. (After Salter and Burmeister.) 
World or the New. 
The sfecies, however, are distinct ; and the 
