Sand Formation of the United States. 291 



may we not with confidence resort to similar data to ascertain the 

 contemporaneous deposits of former ages ?* 



Again, I would ask — if the genera Ammonites, Baculites, Scaphites, 

 Belemnites, Alcyonium, Spatangus, &;c.&:c. are of tertiary origin, by 

 what zoological aids are we to recognize and distinguish the true sec- 

 ondary strata ? The truth of the matter appears to be simply this : if 

 these marl fossils are really referrible to the tertiary class, then there 

 must be an end of geological distinctions founded on organic remains ; 

 and that beautiful system which was erected by Mr. William Smith, 

 and which has since been sustained by the abilities of Cuvier, Brong- 

 niart, Phillips, Conybeare, and many others, must be abandoned as 

 delusive. 



Previous to taking leave of this part of my subject,! beg permission 

 to quote an illustrative paragraph from the writings of Conybeare and 

 Phillips, with respect to the London clay, to which particular divis- 

 ion of the tertiary. Prof. Eaton refers the marl of New Jersey, &c. 



" The testaceous moUusca [of the London clay] are very nume- 

 rous and beautifully preserved, and often retaining nearly the appear- 

 ance of recent shells. There are very few genera of recent shells, 

 which have not some representation imbedded in this formation, but 

 the specific character is usually different ; that difference being often, 

 however, so minute as to escape an unpractised eye. On the con- 

 trary, but few of the extinct genera, so common in the older forma- 

 tions, occur in this ; so that it seems to hold a middle character in 

 this respect between the earlier and more recent beds. Thus, al- 

 though Nautilites, resembling those of the Indian seas, are common, 

 specimens of the Cornu ammonis and Belemnite are so rare, that it is 

 in a very high degree doubtful if they have ever really been found. 

 Echinites, so common in the chalk, are very rare in this formation. 

 Zoophytes are likewise extremely rare."f 



These observations, (which are confirmed by all the more recent 

 works on the subject which I have seen) considered in connexion 

 with the facts detailed in the preceding synopsis, render it extremely 



* The geological analogies between America and Europe are conspicuous in all the 

 formations. Vide Prof. Buckland's note in Amer. Journal of Science, Vol. IV. p. 

 186. See also the very interesting observations contained in Chap. I. of Mr. Ma- 

 clure's Geology of the U. S. 



\ Geology of England and Wales, p. 28. See also the observations of Mess. Cu- 

 vier and Brongniart, on the calcaire grassier, which is now admitted to be contem- 

 poraneous with the London clay. 



