Ferruginous Sand Formation. 129 



Delaware Canal, they offer no answer to this question ; nor, so far 

 as I am informed, have any subjacent deposits of a different age, 

 been any where detected on this continent. 



If it should be hereafter proved that the northern part of our 

 cretaceous group rests on primitive rock, it will be similarly cir- 

 cumstanced to the same formation in Sweden, where, according to 

 Mr. Nilsson, the chalk is generally incumbent on gneiss. Again, 

 in the Carpathian Mountains, the chalk and granite are in immediate 

 contact.* 



Mr. Conrad, who is now on a geological tour in the Southern 

 states, has made some interesting observations near the town of Wil- 

 mington, N. C, which 1 shall give in his own words : "At this place 

 I found the upper marine formation resting immediately on secondary 

 limestone, precisely like that you have described as overlying the 

 marl of New Jersey : it is in thin layers, and reposes on a hard 

 rock, which is the equivalent of the marl itself, as it abounds in 

 Exogyra costata and other characteristic fossils. The calcareous 

 strata are said by intelligent persons here, to extend sixty miles up 

 Cape Fear River, and from its mouth coastwise as far north as Cape 

 Hatteras." 



It seems, therefore, that the calcareous and arenaceous strata of 

 the American cretaceous group, preserve, wherever they have been 

 examined, the same relative position as the white chalk and ferru- 

 ginous sand of Europe. 



Mr. Conrad has also discovered an extensive basin of the calca- 

 reous deposit between Charleston and the Eutaw Springs, in South 

 Carolina ; and it will probably be found, especially in the Southern 

 states, to constitute by far the largest portion of the series, which 

 latter would, in consequence, be more appropriately designated as 

 the Cretaceous group. 



ORGANIC REMAINS. 



CLAVAGELLA. 



C. armata. (S. G. M.) PI. IX, fig. 11. 



Disk obtusely compressed, divided by an irregular fissure, and 

 armed with four or five tubular spines ; two or three other spines be- 

 low the disk : bivalve, concentrically striated. 



* De La Beche, Geolog. Manual, pp. 256, 262. 



Vol. XXIV.— No. 1. 17 



