I9II.] ATLANTIC AND GULF COASTAL PLAIN. 309 



the remains of a typical mangrove flora associated with types which 

 today characterize the tropical and subtropical beach jungle. This 

 flora includes an Acrostichum closely allied to the modern Acro- 

 stichnm aureum Linne which is such an abundant fern in the man- 

 grove and nipa tidal swamps. Other genera represented by fossil 

 forms are Conocarpus, Dodoiicra, Ficus, Malapanna, Pisonia, 

 Momisia, Rhizophora, Sapindus, TcrminaUa, and palms of the genus 

 Thrinax. Botanists familiar with the flora of the torrid zone will 

 recognize at once that this is a typical strand flora of the tropics 

 which might almost have been taken bodily from Schimper's classic 

 Indomalayan Strand Flora, or which can be seen today along the 

 Florida Keys and in the West Indies. 



The plants of this age from ^Mississippi and Arkansas do not 

 indicate such a well marked ecological group nor quite such high 

 temperatures as those from Georgia, nevertheless they also are 

 largely subtropical coastal types and embrace species of Sabal, 

 Rhamnus, Panax, Ficus, Dryandroides, Persea, Sapindus, etc. One 

 of the most interesting forms abundantly represented in north- 

 eastern Arkansas is a citraceous form with alate petioles which I 

 have named Citropliylluni. Additional genera which are present are 

 Nectandra and the coniferous genus Arthrotaxis. 



In Fig. 2 is shown the approximate position of the shore line 

 along which the mangrove and the tropical beach flora migrated 

 northward in the path of northerly flowing tropical ocean currents. 



L'ppER Eocene. 



No upper Eocene floras are known from the coastal plain but 

 it is believed that future discovery will reveal their presence when 

 the area where they are likely to occur shall have been examined 

 in detail. 



Lower Oligocene. - 



The Lower Oligocene has yielded no plants except petrified 

 fragments of the wood of palms and dicotyledons. The sediments 

 are more or less impure marine limestones, and if marginal deposits 

 with plants were laid down they were subsequently destroyed by 

 erosion, or have not yet been discovered. 



