127 



Prunus. Naturally a single stone (pit) is not much of a basis for 

 a new species, but the likelihood of finding even a second speci- 

 men is remote. 



The genus is widely distributed in modern floras of the North 

 Temperate Zone with about 125 species and many cultivated 

 varieties. Baillon segregated it in 9 sections and Focke uses 

 seven. Several of these, e.g. Amygdalus are undoubtedly entitled 

 to generic rank. The fossil obviously does not belong to the 

 plum, almond or peach tribes but might well be related to the 

 cherries. 



No useful comparisons with existing species are possible nor 

 does the fossil appear to be close to any of the existing North 

 American species, but it is impossible to get far with the stones 

 alone, nor de we know the factors making for rugosity, although 

 some authors are inclined to think it has a relation to increased 

 size of the fleshy exocarp, and this is partly borne out by the 

 features in horticultural hybrids. 



No leaves of Prunus are known from the Miocene of eastern 

 North America. Without checking the identifications it may be 

 said that about 80 fossil species of Prunus have been described 

 ranging in time from the Upper Cretaceous through the Pleisto- 

 cene and reaching a maximum in the Miocene. They are all 

 confined to the Northern Hemisphere, and beginning with the 

 Eocene a considerable number, about half the total known, are 

 represented by fruits. Among these the one which appears most 

 similar to Prunus calvertensis , although it is doubtful if this 

 is of any real significance, is a form from the Pliocene of Swal- 

 men, Holland which is referred by the Reids to Prunus spinosa 

 Linne. 



Locality: Nomini Cliffs (blufif named Horsehead on Coast 

 Survey Chart). 



Horizon: Zone not determined. 



Collector: Charles T. Berry, June, 1935. 



Johns Hopkins University 

 Baltimore, Md. 



