TABLE OF CONTENTS 



Page 



TITLE PAGE, i 



TABLE OF CONTENTS, 3 



INTRODUCTION 5-12 



DISCUSSIONS OF THE SPECIES 13-95 



Crania siluriana, Hall, ........ 13 



Orthis elegantula, Dalman, ........ 13-17 



Orthis hybrida, Sowerby, . . . . . . . . 17-18 



Strophomena rhomboidalis, Wilckens, ...... 18-22 



Streptorhynchus subplanum, Conrad, ...... 23-25 



Strophonella striata, Hall, ........ 25-29 



Streptis waldronensis, Miller and Dyer, ..... 30-31 



ElCHWALDIA RETICULATA, Hall, ........ 31-32 



Anastrophia internascens. Hall, ....... 32-34 



Rhynchonella acinus, Hall, ........ 35-36 



Rhyjjchonella neglecta, Hall, ....... 37-39 



Rhynchonella whitii, Hall, 39-42 



Rhynchonella indianensis, Hall, ....... 42-47 



Rhynchotreta cuneata, (Dalman) var. Americana, Hall, . . . 47-51 



Atrypa reticularis, Linnaeus, ....... Si-S5 



Retzia evax. Hall, . . . . - . • . . . . 55-61 



Retzia sobrina, sp. n., . . . . . . . . . 61-64 



Ccelospira disparilis, Hall, ........ 64-67 



Meristella rectirostra. Hall, ....... 67-69 



Meristina nitida, Hall, ......... 70-72 



Whitfieldia MARIA, Hall, ........ 73-75 



Spirifer crispus, Hisinger, 75-77 



Spirifer crispus, var. simplex, Hall, ...... 75-77 



Spirifer bicostatus, (Vanuxem) var. petilus. Hall, . . . 75-77 



Spirifer radiatus, Sowerby, ........ 77-8i 



SUMMARY OF DEVELOPMENTAL CHANGES 83-95 



PLATES AND EXPLANATIONS, I-VIII 97 



