256 Prof. Rogers's Address before the 



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 that state, to the vicinity of 

 Piscataway, a few miles south of Washington. The great thickness of 

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

 most exclusively of the siliceous cases of minute infusorise, 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 miderlaid 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 of 

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

 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 to this time he has observed fifty 

 two forms, among which are about forty six infusoria belonging to 

 twenty genera, which genera are all European with the exception of 

 two, Goniothecium and Rhizosolenia, which have not been observed at 

 any other locality. Of the species, ten, or almost one ffth, are new 

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

 Bailey quite correctly concluded from his smaller number of observa- 

 tions, similar to those of Oran, but many of these forms also do not 

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

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

 found at Richmond alone, and one at Oran alone." 



" As a considerable number of the species of animals belonging to 

 the chalk formation of Sicily still exist and consequently cannot be 

 wanting in the tertiary formations, it is evident that no conclusion as to 

 the geological age of these formations, can be drawn from the simi- 

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

 group of American forms is of peculiar interest and scientific import- 

 ance, because the strata at Richmond are decidedly of marine origin 

 and consequently give at once a general view of the marine microscopic 



