REPORT OX THE GEOLOGY OF NORTH AMERICA. 51 



however, mainly due to Mr. Conrad, have shown it to exist in 

 nearly all the Southern States ; and from specimens brought, 

 from time to time, from the interior of the continent, it would 

 appear to occur abundantly on the Missouri far across towards 

 the Rocky Mountains. From observations made by Professor 

 Hitchcock upon the clay and satid strata of Martha's Vineyard, 

 there seems little reason to doubt its existence either beneath 

 that island or somewhere in the vichiity ; and it is more thaii 

 probable, from appearances, that it underlies Long Island. " It 

 is first unequivocally seen in New Jersey, whence it may be 

 traced locally through Delaware, Maryland, Virginia, North 

 and South Garohna, Georgia, Alabama, Mississippi, Tennessee, 

 Louisiana, Arkansas, and Missouri." Dr. Morton remarks that 

 " these various deposits, though seemingly insulated, are doubt- 

 less continuous, or nearly so, forming an irregular crescent nearly 

 three thousand miles in extent ; and, what is very remarkable, 

 there is not only a generic accordance between the fossil shells 

 scattered through this vast tract, but, in by far the greater num- 

 ber of comparisons I have hitherto been able to make, the same 

 species of fossils are found throughout : thus, the Ammonites 

 placenta, Bamlites ovatus, Gryphcea Vomer, Ostrea falcata, 

 Exogyra, &c., are found without a shadow of difference from 

 New jersey to Louisiana, although some species have been found 

 in the latter state that have not been noticed in the former, and 

 vice versa." 



Calcareous Formations. — Beds of limestone and calcareous 

 sandstones form the upper strata of the secondary class through- 

 out the greater part of the marl region, as it is called, of New 

 Jersey. They always occur in thin, horizontal, and rubbly lay- 

 ers, either interstratified with blueish clay, or more commonly 

 resting immediately upon the friable sands and marls of the 

 formation beneath. The more calcareous beds are often highly 

 fossiliferous and partially crystalline, reminding me strongly in 

 their stratification and general appearance of some of the com- 

 pact and thin oolites of England. Dr. Morton describes these 

 calcareous strata as presenting the following varieties, — 



"An extremely friable mass, containing at least 37 per cent. 

 of lime, with a considerable proportion of iron, silex, &c. It 

 appears to be almost entirely composed of disintegrated zoo- 

 ph^'tes — 



"A yellowish or straw-coloured limestone, as hard as the car- 

 boniferous varieties, containing numerous organic remains, — 



" A granular or subcrystalline limestone, intermediate in 

 structure between the former two, and including similar fos- 

 sils. 



