3o6 



GEOLOGICAL BIOLOGY. 



Fig. 83 



Fig. 85. 



Fig. 87. 



Fig. 92. 



Fig. 89. 



Fig. 90. 



Fig. 91. 



Fig. 94. 



Fig. 95. 



Figs 83-05.— Modifications of the surface features of the Spirifers, expressed in the species of the 

 Niagara period. (After Hall.) 83. Sfiiri/er radiatus Sow. 84, 85. 5. plicatelUi Linn. 

 86. S. eudora Hall. 87. 6'. hfiagare nsis HaW. 88. S crispus His. 89. .s. sulcatum His. 

 90'. S. buostatus Hall. 91. .V. tenuistriatus H. 92. Enlargement of the surface of S. ens- 

 pus. '93. Surface, enlarged, of 5. sulcatus. 94. Surface, greatly magnified, of S. Niagaren- 

 sis. a--.. Enlartrement of surface of S. eudora. 



