14 Secondary Fossils. 



vata, Physa, and others, are at once carried down from the 

 eocene group to the oolite, and such a fact should for ever 

 warn us against reasoning in future on mere negative evi- 

 dence, as to the non existence of all similar families of mol- 

 lusca in the primary periods. 



In speaking of the Vertebrata of the secondary rocks, I 

 need only observe respecting the fish and reptiles, that they 

 were most fully developed in their organization, the Iguano- 

 don and some other contemporary saurians making even a 

 nearer approach in many characters of their osteology to 

 warm-blooded quadrupeds than any reptiles now living on 

 the globe. The only points therefore in secondary palaeon- 

 tology to which it seems necessary to allude, are, first, the 

 foot-prints of birds in the trias of North America; secondly, 

 the fossil mammalia of the Stonesfield oolite ; and thirdly, 

 the extreme scarcity, if not entire dearth, at present, of ceta- 

 ceous remains in rocks older than the eocene. 



First, as to the age of the red sandstone containing bird- 

 tracks in the valley of the Connecticut river, I have little 

 doubt that this rock is at least as old as the European trias. 

 It contains several species of fossil fish of the ganoid genus 

 Ischypterus of Egerton, by which it is distinguished from 

 those coal-bearing strata of oolitic or liassic age, near Rich- 

 mond in Virginia, which I have described in the third volume 

 of your Quarterly Journal. The genus Ischypterus is of a 

 peculiar type, and therefore of small value in settling a chrono- 

 logical question, but the want of a decidedly heterocercal tail 

 may perhaps raise some presumption against their being 

 Permian. That they are newer than the true or primary 

 coal measures may be deduced from still more satisfactory 

 data. The old carboniferous formation enters into all the 

 flexures of the Appalachian chain, whereas the red sandstone 

 of the Connecticut, or at least its equivalent in New Jersey, 

 reposes in many places unconformably on the denuded edges 

 of the inclined or vertical Appalachian beds. 



When I first examined these strata of shale and sandstone 

 near Jersey city, in company with Mr Redfield, I saw at once 

 from the ripple-marked surface of the slabs, from the casts 

 of cracks, the marks of rain-drops, and the imbedded frag- 



