468 



BIDDULPHIA. 



a. t. 



Fig. 202. B. ( Ceraiaulus ) Smithii. 

 a. Valve view. b. Girdle view. 



Fig. 203. B. ( ' Pseudo-stictodiscus) 

 Eulcnstcinii. 



b. 



c. 



a. Girdle view. 



Fig. 204. Z?. (Tricerdtium) Favus. 

 b. Portion of valve with puncta x 1000. c. Valve view. 



