A REVIKW OF THE FOSSIL OSTREIDil OF NORTH AMERICA; 

 AND A COMPARISON OF THE FOSSIL WITH THE LIVING 

 FORMS. 



By C. a. White. 



INTRODUCTION. 



Because of the great value of the commou oj'ster as a favorite article 

 of food, perhaps uo subject connected with fossil conchology will be 

 found to possess more interest to the general reader than that of the Os- 

 treidiE, or oyster family. With this supposition in view I propose to 

 jiresent on the following pages a general review of that family as it is 

 represented among the collections of fossil remains that have been made 

 from North American strata. In addition to a general statement of the 

 subject, with illustrations of the fossil forms, I shall give, for comparison, 

 figures of the leading varieties of the oysters that are now found living 

 upon our Atlantic coast. I had intended to illustrate the living oysters 

 of the Pacific coast also, but I found it impracticable to obtain good 

 specimens of them. 



While much is known concerning the geological history of the oyster 

 family within the area that now constitutes the North American conti- 

 nent, that history is and will doubtless always remain incomplete. This 

 incompleteness is due mainly to the fact that among the fossil forms it 

 is the shells alone that are available for study and to the further fact 

 that these remains are usually few and very often too imperfect to ex- 

 hibit all the characteristics which perfect shells possess. Besides this, 

 the extreme variation in the form and other characteristics of the shell 

 of the fossil, as well as the living Ostreidfe, renders their separation into 

 species, and even into genera, a matter of much uncertainty. In the 

 case of most other bivalve shells there is a certain precision of symme- 

 try that is constant in every individual, from the earliest to the latest 

 stage of its growth ; but among the Ostreidte, and especially in the 

 typical genus Ostrea, asymmetry of the shell is the invariable rule. To 

 what primary cause this a symmetry among the Ostreidie is due, it is, 

 with the present limitation of our knowledge, impossible to say ; but it 

 is certainly a characteristic of the whole family, including all its genera 

 and its fossil as well as living terms. 



The oyster family belongs to that division of the bivalve mollusca 



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