OF THE UNITED STATES. 83 



CONCLUSION. 



It is well known that there is at present a remarkable 

 generic accordance, between the testaceous mollusca of the 

 eastern and western shores of the Atlantic ocean ; and by 

 a reference to No. 2 of the Appendix, it will be seen 

 that at least twenty-four species of shells have already been 

 identified as common to both. Is it not probable that this 

 accordance was formerly as great as at present ? It will 

 be hereafter seen that I have also traced some identities 

 in the tertiary deposits of Europe and America ; and 

 when we arrive at the Cretaceous group, the highest of 

 the secondary series, we find the Pecten quinquecosta- 

 tus, (which has been aptly called the " finger post" of 

 the chalk formation,) as frequent as it is unequivocal, on 

 both sides of the Atlantic. Although I have been un- 

 able to satisfy myself of any other identities in the widely 

 separated portions of this series, yet the analogues are 

 surprisingly obvious, and may be judged of by a mere 

 glance at the accompanying plates. 



Again, the analogy is not confined to the Testacea, but 

 is observed in the great family of the Saurian reptiles ; for 

 there is no perceptible difference between the teeth of 

 the Mosasaurus of Europe and'that of New Jersey. From 

 these and other data scattered through this work, I arrive 

 at the conclusion, that when the chalk fossils were living 

 inhabitants of the seas of Europe, the organic relics of 

 this synopsis were alive in the ocean of America ; in 



