144 



HISTORICAL PALEONTOLOGY. 



in many specific forms (figs. 86 and 87) ; but almost all the 

 known examples are of small size, ar.d are liable to escape a 



cursory examination. 



The Crustaceans of 

 the Devonian are prin- 

 c i pal I y Eurypterids and 

 Trilobites. Some of the 

 former attain gigantic 

 dimensions, and the 



Fig. 87. a, Sfiirorbis ovtfihalodes, natural size qimrrvmen intlieScOtcll 

 and enlarged, Devonian, Europe and America ; Ai j T j ,1 ,1 



b, Spircrbis Arkonensis, of the natural size and U* r^O. glVC them the 

 enlarged ; c, The same, with the tube twisted in 

 the reverse direction. Devonian, America, (Ori- 

 Cinal.) 



name of " seraphim/' 

 from their singular 

 scale - like ornamenta- 

 tion. The Trilobites, 

 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. a b, Spirorbis laxns, enlarged, Upper 

 Silurian, America; c, Spirorbis spinnlijera, of the 

 natural size and enlarged, Devonian, Canada. (Af- 

 ter Hall and the Author.) 



Fig. 88. Devonian Trilobites n, Phaeops lat!/rons,'Dzvo-n\a.n of Britain, the Conti- 

 nent of Europe, and South America ; b, Homalonotus armatns, Europe ; c, Phacops 

 (Trimerocephalns) Icevis, Europe; d, Head-shield of Phacops (f'ortlockia) granulatns, 

 Europe. (After Salter and Burmeister.) 



World or the New. The species, however, are distinct ; and the 



