PLATE II. 



MONOMERELLA KiNGI, Hall. 



Page 329. 



Fig. 1. An internal cast of a pedicle-valve ; showing the very short umbonal 

 chambers and the sharply defined muscular impressions. 



Fig. 2. Opposite side of the same specimen ; showing the internal character* 

 of the brachial valve . 

 Niagara limestone . Hawthorne, Illinois. 



MONOMEBELLA EgANI, Hall. 

 Page 330. 

 Fig. 3. A brachial valve ; showing the strongly developed cardinal area, the 

 narrow crescent and the platform scars. The umbonal cavity is filled by 

 a thick deposit of testaceous matter. 

 Niagara limestone. Grafton, Wisconsin. 



MONOMEEELLA OeTONI, Hall. 



Page 330. 



Fig. 4. An internal cast of the pedicle-valve, in which all the characters of 

 the shell are very sharply defined . 



Fig. 5. The counterpart of the same from a gutta-percha impression; show- 

 ing the broad deltidium without evidence of subdivision, the conspicuous 

 cardinal slope and groove, the crescent and platform scars and the pallial 

 trunks with their ramifications. 

 Niagara limestone . Rising Sun, Ohio . 



Rhinobolus Davidsonii, Hall. 



Page 331. 



Fig . 6 . The interior of a brachial valve . 



Fig. 7. The interior of a larger brachial valve; showing the undeveloped 

 platform, the crescent and the transverse muscular scars. 



Fig. 8. A small pedicle- valve, showing its internal characters. 

 Niagara limestone . Grafton, Wisconsin. 



SiPHONOTEETA (?) MiNNESOTENSIS, Hall. 

 Page 332. 

 Fig. 9. View from the brachial side of a specimen retaining the valves in jux- 

 taposition, and preserving most of the epidermal layer of the shell. The 

 spine-bases about the beak are notably larger and more closely set than 

 over the rest of the surface, where they occur at considerable intervals 

 along the concentric varices. The entire Ifength of the spines is evidently 

 not represented in the fringe at the margin. X 2. 



376 



