PLATE LXXXIII. 



Ptebixopectex begulaeis. 



Page 70. 

 Fig-. 1. A left valve showing- the characteristic form and surface markings. 

 Hamilton group. Livingston Cv.. N. Y. 



Ptebixopectex Yektu.mm s. 



Page 71. 

 See Plat.- 5. 

 Fig-. 2. A small specimen preserving- the left valve entire and a portion of the right vah e. 



Hamilton group. Onondaga Co., N. Y. 

 Fig. 3. A left valve to show the characters of the surface ornamentation. 

 Hamilton group. Skaneateleslake, N. V. 



Pteuixopectex intermedius. 



Page 68. 



See Plate 17. 

 Fig. 4. A left valve wholly denuded of the test. 



Hamilton group. Cayuga lake. 2V. Y. 

 Fig. 5. A left valve as obtained from an impression of t lie exterior in the matrix, showing the form an. 

 surface markings. 



Hamilton group. Cayuga lake. IV. Y. 



