44 



Bulletin i 4 



310 



BLACK RIVER AND TRENTON FOSSILS 



Explanation of Plate 19 



Page. 

 Fig. I. Bathyurus spiniger Hall. A glabella showing 

 tubercles and the faint lateral grooves. 

 Black River. 



2. Pygidium of the same, shovi^ing the base of the 



spine and the tubercles on the end of the 

 axis. 



3. Side view of the same. 



4. Triplecia exta^is Emmons. Dorsal valve of a 



large individual. Black River 38, 304 



5. PleRorthis plicatella Hall. Cast of the ventral 



valve, showing muscular scar. Black 



River 38, 304 



Cardinal areas of the same, showing pedicle 



opening. 

 RapJiistoma lenticulare Emmons. Side view of 



cast. Trenton limestone 40, 3^^ 



Top view of the same. 



Bucania pun5lifrons Emmons. Side view of a 



medium sized specimen. Trenton. 

 Another view showing surface markings and 



carina. 

 Strophoniena hicurvata Shepard. Interior of a 



ventral valve. Black River 37, 303 



12. Pterotheca expansa Emmons. Trenton 40, 306 



