144 



HISTORICAL PALEONTOLOGY. 



in many specific forms (figs. S6 and 87) ; but almost all the 

 known examples are of small size, and are liable to escape a 



cursory examination. 



The Ci'ustaceans of 

 the Devonian are prin- 

 cipally Eurypterids and 

 Trilobites. Some of th e 

 former attain gigantic 

 dimensions, and the 

 quarrymen in the Scotch 

 Old Red give them the 

 name of *' seraphim," 

 from their singular 

 scale - like ornamenta- 

 tion. The TiHlobites, 

 though stiU 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. 87. — a, Spi7-orhis ompJialodes, natural size 

 and enlarged, Devonian, Europe and America ; 

 b, Splrorbis Ayko^iensis, of the natural size and 

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

 the reverse direction. Devonian, America. (Ori- 

 ginal.) 



Fig. 88. — a b, Spirorbis laxus, enlarged. Upper 

 Silurian, America ; c, Spirorbis spinulifera, of the 

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

 ter Hall and the Author.) 



Fig. 88. — Devonian Trilobites a, PJiacops lati/rotts, Devonian of Britain, the Conti- 

 nent of Europe, and South America ; b, Hotnaionotiis annatus, Europe ; c, Phacops 

 (TrimerocepJialus) Leins, Europe; d. Head-shield of Phacops (Portlockia) granulattts, 

 Europe. (After Salter and Burmeister.) 



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



