PLATE 46 



Chonetes melonicus Billings 



Page 206 



1 Dorsal view of an impression of the exterior. Billings's original 



2 Internal cast of a ventral valve, showing place of septum and muscle 



scars. X 2 



3 A portion of the dorsal valve, viewed from without, showing the 



cardinal process, x 3 



4 Exterior mold of the dorsal valve 

 Grande Grtve limestone. Grande Greve 



Chonetes antiopa Billings 



{See plate 45) 

 Page 208 



5 Exterior of a ventral valve, x 3 

 Grande Greve limestone. Grande Greve 



Chonostrophia complanata Hall 



Pages 210, 241 



6 A small ventral valve with cardinal spines, x 2 

 Grande Greve limestone. Perce Rock 



7 Internal cast of a ventral valve, showing the course of the cardinal 



spines, x 3 



8 Internal cast of the ventral valve with muscular scars 



9 A similar view of the ventral valve 



10 Enlargement of the interior pallia! surface, x 5 



1 1 A ventral valve 



12 Enlargement of the exterior showing the character of the striation. x 5 



13 A small ventral valve 



Grande Greve limestone ; divisions i, 2. Grande Greve 



Chonostrophia dawsoni Billings 



Page 240 



14 A small ventral valve with full array of spines 



15 The external surface, x 5 



344 



