PLANT LOCALITIES. 2{) 



It is quite probable tliat Meek's specimens come from that higher horizou 

 wliicli yielded fossils to Professor Uhler, from wliose description it would 

 appear that they belong to the lower Potomac flora, as is the case witli 

 Meek's j)lauts. 



It is j)robable, then, that all the plant-impressions found at Baltimore 

 belong to the lower member of the Potomac formation, none coming from 

 the upper one, or the Variegated Clay. 



The spot where I obtained the plants belongs to the southeast slope of 

 Federal Ilill, and is situated on Covington street, east side, sevonty-five 

 feet north of Cross street. 



Since my visit additional collections have been made by Professor 

 Uhler and Prof Lester F. Ward at the Covington-street locality and on 

 Belt street. They have been placed in my hands for study, and form a por- 

 tion of the plants described further on. 



The Belt-street locality is on that street, next to and directly north of 

 Ellicott's iron furnace. It is situated two squares southeast of the Coving- 

 ton-street locality. The fossils at both spots occur in the clay layers im- 

 mediately above the sand of the lower Potomac, the lowest rock visible. 

 At the Belt-street locality Professor Uhler obtained the best specimens of 

 Cclastro2)hi/llitin and Aclirotitkhopfeiis that were found. 



The doubt that exists as to the true horizon of the plants formerly 

 found in Maryland arises from the fact that no one who collected them was 

 aware of the existence of the lower Potomac under tlie Variegated Clays 

 and of the existence of gray clay in the top of the former, or else, if this 

 fact was known, the difference in the age of the two was not perceived. 



All the gray clay along the lialtimore and Oliio Railroad between 

 Washington and Baltimore and at the latter place was supposed to belong 

 to the Variegated Clay group. The base of this group seems to be formed 

 of material derived from the erosion of the argillaceous upper poition of tlie 

 lower Potomac. There is, then, no marked difference in the composition 

 of the uppermost of the lower Potomac and the lowest of the Variegated 

 Clay system. It follows, then, that fossils attributed by former collectors 

 to the lower portion of the Variegated Clay may really come from the top 

 of the lower Potomac. 



