30 Annals of the Carnegie Museum. 



5. The Mud-swamp Formation. 



Probably the nearest approach to this formation in the region 

 explored by the writer is the muddy margin of the pond about one 

 and one-half miles east of Nueva Gerona. One of the most striking 

 plants is Odontosoria Wrightiana forming large clumps or tussocks, 

 much in the same manner as does Osmunda cinnamomea in our North- 

 ern swamps. 



6. The Strand Formation. 



The strand formation is well developed near Bibijagua, and at 

 that place it may be seen to consist of three well-defined members, 

 as follows: 



(a) The Ipomma Pes-Caprce Association characterized by the beach 

 morning-glory {Ipomcea Pes-Caprce). (See Plate V.) 



(b) The Suriana- SccBvola Association characterized by Suriana 

 maritima and Sccevola Plumierii. 



(c) The Coccolohis uvifera Association. The sea grape is some- 

 times supplanted in such locations by the poisonous Metopium 

 Brownei, as at Siguanea Beach. 



7. The Salt-marsh Formation. 



Very little salt-marsh was seen on the Isle of Pines. Near the 

 mouth of the Nuevas River there was a small area of it and some 

 of the halophytic swamp between the northern and southern portions 

 of the island probably should be so classed. Photographs taken up 

 the channels of this swamp by Dr. D. A. Atkinson show Mariscus 

 jamaicensis to be apparently a characteristic member of this salt 

 marsh. Distichlis spicata is also a member of this formation. 



8. The Fresh-water Marsh Formation. 

 This formation is probably represented in the middle portions of 

 the swamp mentioned above, but it was not personally studied. 



9. The Sand-plain Formation. 

 Near the mouth of the Nuevas River there are areas probably 

 derived from a salt-marsh by the accumulation of loose sand. This 

 is perhaps best characterized by Andropogon tenuispathaceus and 



includes Opuntia. 



10. The Savanna Formation. 



This is one of the most prominent and characteristic formations on 

 the island, occupying most of the lower areas of the plain, excepting 



