PLATE IX. 



Unless otherwise stated, all the figures are of natural size. 



MONOMERELLA DUEHAMENSIS (page 57). 



Figure 1. The larger portion of the specimen described, showing the cardinal 

 area of the pedicle valve and the cast of the interior of the brachial 

 valve. The other part of this specimen is represented on Plate 

 XV., fig. 1. 



Rhinobolus Galtensis (?) Billings. Var. (page 61). 



Figure 2. Exterior of the pedicle valve of the only specimen known to the writer 

 " 2a. Interior of the same. 



Pentamekxjs occidentalis, Hall (page 65). 



Figure 3. Dorsal view of an unusually perfect specimen of this species. 

 " 3a. Lateral view of the same. 



