Till-: MAHYLAXn CVCADS. 41.") 



employed by llie residents in dcscrihinfr them. A few of the frajrmeiits ai'e 

 suggestive of considerable elongation not unlike tliat of the niodein 

 Cyca.^ rcrolnfa or Macrozaniia. In these cases, ho\ve\'er, tlie siiape of the 

 tnmk appears 1o be governed to some extent by the food supply — uni- 

 foi-mity producing a regulai'ly cylindrical tr'nnk. and want of it an ii'i'egulai' 

 conical one. 



The so-called "crow's nest" is in a few cases very well defined. The 

 1)est of these occurs in the Turner trunk (PI. XCV), which, ;is ali'eady 

 stated, was long in use as a watering trougli for domestic fowls. 



The considerably weathered and etched condition of the fi-acttu-ed 

 surface of most of the fi-agments indicates that the fi-actures are of con- 

 siderable age. This conclusion I'eceives some confirmation by the fact 

 alread>- suggested that, save in a single instance (W. C. B. Nos. 1659 and 

 1659a), a second fragment has nevei- been found near the first. In the 

 case of the exception the fracture is evidently- not recent, as supposed 

 by the plowman who unearthed it, and this is the only instance in which 

 two fragments have ever matched together. 



The color of the trimks is identical with that of the silicified coniferous 

 w^ood which -is not unfrequently associated with them. When newly 

 unearthed they are light and dark Iniff' to reddish Ijrown or brownish red, 

 dependent upon the amount of hydrous iron oxide present in their original 

 or secondary beds. After exposure to the weather for some time they 

 are apt to assume darker tints — light and dark gray being the most 

 common. 



Respecting the frequency of occurrence of the Potomac cycad trunks, 

 it .should be stated that, while the number of specimens which have been 

 brought to light within a comparatively short time is considerable, this 

 is due rather to the adoption of a successfid method of searching than 

 to the actual abundance of the fossils. They are really so scai'ce that there 

 is little chance of one being secured from the field by direct search. Xo 

 one, in fact, has ever been known to do this, all having thus far been 

 found by accident. It is rarely that more than one trunk has been noted 

 in a given locality, l)ut there are a few notable exceptions to this rule. 

 Though the cycad tmmks are of considerably less frequent occurrence 

 than the silicified trimks of conifers, it may be said that there was a 

 goodly showing of the cycadaceous vegetation in the forests of Potomac 

 times. 



