EXPLANATION OF PLATE 31 



Fig. A. Specimen of red radiolarian chert showing leaching along fissures. 



Fig. B. Pebble of red chert, showing the type of curving quartz veinlets 

 which are developed at the contact with igneous rocks. 



Fig. C. Chert rendered massive by contact action with development of net- 

 work of quartz veins. 



[ 422 | 



