246 



PALEOZOIC TIME. 



of the three figures) which constituted the hard rough skin (shagreen) 

 of a shark. A number of Upper Silurian fishes have been described, 



Figs. 477-482. 



Fig. 477>0mphyma turbinatum ; 478, Cystiphyllum Siluriense ; 479, Crotalocrinus rugosus ; 480, 

 Pentamerus Knightii ; 481, Grammysia cingulata ; 482, 482 o, Pterygotus bilobus. 



from the rocks of Russia and Bohemia, including species of Coccosteus 

 and Pterichthys, and the fin-spines of sharks ; figures of other species 



Fig. 483. 



Fishes. — Fig. 483 a, Pteraspis Banksii, tail-shield ; 483 b, Cephalaspis Murchisoni, inside of head- 

 shield ; c, spine of Onchus tenuis triatus ; d,Plectrodus mirabilis ; e, Shagreen pieces of Thelodus 

 parvidens. 



of these genera are given on p. 285. For further remarks on the 

 subdivision to which these fishes belong, see page 264. 



