142 



PAL/EONTOLOGY. 





front terminal or rostral plate ; it is followed in the median 

 line by four other plates in the following order : — 4» preme- 



Fig. 59. 

 Pterichthys, dorsal surface (Devonian), after Pander. 



dian; 6, median; %, postmedian ; io, nuchal; 3 is the marginal, 



