PLATE XXI. 



I'aga 

 Cardium (Ckiocardium) multiradiatum Gabb 135 



Fig. 1. Lateral vi<'W of a well-preserved cast of this species. 



2. Cardinal view of the same. 



3. EDiargement of a fragmeut of the matrix, showing the character of ribs and the 



spines which rise from the depressions between them, as obtained from a gutta- 

 percha impression. 



Cardium (Protocardilm) perelongatum Whitfield 1S6 



Figjs. 4 and 5. Views of a large cast from the collection of the Academy of Natural Sciences 

 of Philadelphia, showing the general form. 



Pachycardium Burlingtonense Whitfield 138 



Figs. 6 and 7. Views of the cast described, showing the remains of the strong, heavy ribs, 

 and the large musciihjr scars. 



310 



