388 MESOZOIC FLORAS OF UNITED STATES. 



It is veiy possible that all except the Potomac beds in this section 

 may belong to the Pleistocene formation (Columbia). 



The specimens collected dming the season of 1893, and other small 

 collections previously made from Older Potomac beds, were sent to Pro- 

 fessor Fontaine on October 28, 1893, but he could not determine them at 

 the time on account of other work in hand, nnd they are treated in this 

 paper for the first time. In his letter dated January 10, 1894, he remarked 

 that in the collections from Cockpit Point ' ' the grouping is decidedly the 

 same as that found at Fredericksburg. ' ' 



In the first biennial report of the Maryland State Weather Service, 

 which was distributed at the beginning of 1894, its director, Prof. Wm. B. 

 Clark, devotes a chapter to the geology of the State," thus marking the 

 beginning of his subsequent active studies in that line and foreshadowing 

 the organization under his direction of the present State Geological 

 Survey. He here treats "The Lower Cretaceous (Potomac)" (pp. 37-38) 

 very briefly, and concludes with the following remark: 



The fossils found in the deposits, although not as numerous or distinctive as 

 might be desired, yet indicate beyond doubt the Cretaceous age of the formation. 

 They consist chiefly of the bones of dinosaurian reptiles and leaf impressions. 



It was during the first half of 1894 that I prepared my paper on the 

 Potomac formation for the Fifth Armual Report of the United States 

 Geological Survey, and the manuscript and drawings were submitted for 

 publication on June 26. This paper embodied the results of the special 

 field investigations of the previous nine years, a brief account of which 

 has been given here. It can not be called a final report, but must be 

 regarded rather as a preliminary one. Nevertheless, I have not been 

 able to prepare anything more extended, and it represents the state of 

 our knowledge of the formation at that date. The paleontolog)^ was 

 used to supplement and confirm the stratigraphical conclusions, but, in 

 view of the recent appearance of Professor Fontaine's monograph of the 

 flora, the only sj^stematic matter introduced related to the florula obtained 

 from the Mount Vernon clays, which was so different from the general 

 flora that I considered it important to make it known. This paper was 

 read in part before the Geological Society of Washington on March 28 



'I The Climatology and Physical Features of Maryland, First Biennial Report of the Maryland State 

 Weather Service for the Years 1892 and 1893, by Wm. B. Clark, Director, Baltimore, 1894, pp. 29-44. 



