thicknes 



•> 



i 



256 Prof. Rogers's Address before tlie 



* 



discovery made in the wonder field of microscopic life. The remarka* 

 ble infusorial stratum originally detected by my brother on the Rappa- 

 hannock, and at Richmond, Virginia, he has since traced from the Me- 

 herrin river near the southern boundary of thf 

 Piscataway, a few miles south of Washington. 



the stratum, amounting at Petersburg to thirty feet, and consisting al- 

 most exclusively of the siliceous cases of minute infusoria?, but espe- 

 cially the variety and beauty of the many new species brought to light 

 through the skill of Prof. Bailey and Prof. Ehrenberg, invest this de- 

 posit with a high interest. Respecting its geological relations, I would 

 here observe that it is not, as intimated by Mr. Lyell, of eocene epoch 

 but lies, according to the investigations of my brother and Mr. Tuomey 

 within and near the bottom of the miocene strata, being underlaid by 

 unequivocal miocene, both at the Stratford cliffs on the Potomac and at 

 Petersburg. The former suspects, indeed, that the infusorial deposit 

 occupies more than one horizon in the miocene. The following short 

 extract from a recent memoir by Ehrenberg, an interesting notice o 

 which has just appeared in Silliman's Journal, exhibits the palaeonto- 

 logical affinities of this stratum to the infusorial deposits of other re- 

 gions and other geological times. 



After ascribing the discovery of eleven of the species to Prof. Bailey, 



Ehrenberg proceeds to say, that up 



two forms, among which are about forty six infusoria belonging 

 twenty genera, which genera are all European with the excep 1 

 two, Goniothecium and Rhizosolenia, which have not been observe 

 any other locality. Of the species, ten, or almost one fifth, are n 

 and peculiar. " Many of the forms occurring in the deposit are, as 

 Bailey quite correctly concluded from his smaller number ot ods 

 tions, similar to those of Oran, but many of these forms also do » 

 occur at Oran." Thus " of the eleven species of the genus Coscino- 

 discus, five occur at Oran which are also found at Richmond, v 

 found at Richmond alone, and one at Oran alone. 



fifty 



to 



nof 



11 



" As a considerable number of the species of animals belonging 

 the chalk formation of Sicily still exist and consequently cannot 

 wanting in the tertiary formations, it is evident that no conclusion a ^ 

 the geological age of these formations, can be drawn from the si 

 larity or dissimilarity of these forms." He goes on to say, that 



group 



— w 



ance, because the strata at Richmond are decidedly of marine 

 and consequently give at once a genera} view of the marine inicr 



origin 





