GENERAL OBSERVATIONS ON THE FLORA. 



Fossil Plants from the Older Mesozoic of Virginia — Continued. 



93 



We have thus far found in the Mesozoic strata of Virginia forty-two 

 species of plants sufficiently well preserved to be of some value in deter- 

 mining the age of the beds. Twenty-one of these appear to have no very 

 near relations in the European floras. This large proportion, or 50 per cent., 

 of species peculiar to Virginia, will be considerably lessened if we take into 

 consideration the North Carolina plants and the plants found by Dr. New- 

 berry and others in the older Mesozoic strata of Sonora, &c. But, as the 

 age of this latter flora yet remains to be fixed, the plants common to it and 

 the Virginia Mesozoic cannot be considered in any attempt to fix the age 

 of the Virginia strata. This large proportion of species found in Virginia 

 and not found in Europe is a noteworthy fact. Although we do not find 

 specific identity in the case of any of these plants, yet we may get some 

 hints as to their age from their generic characters and probable affinities. 

 Taking up the list in order, then, we may note the following facts. We 

 must omit, of course, the undetermined species of ScMzoneura. It may be 

 the cast of the interior of the S. Virginiensis. 



We find two species of Acrostichides peculiar to Virginia, A. microphal- 

 lus and A. densifolius. It must not be forgotten that these two plants may 

 not be Acrostichides, as their fertile fronds have not been found. There 

 can, however, be little doubt, I think, that they are Acrostichides, for the 

 two types of the sterile forms of Acrostichides are both represented in them, 



