-14- 
(2) An Eocene system composed of a great thickness of impure lig- 
nitic sands and clays like the Richmond beds (of Jamaica), and which 
outcrops near San Sebastian, Guatemala, and Mocha, on the western end 
of the island, and near Carolina on the northeast coast. 
(3) Fossi sli ferous greensand marls of undetermined age (Eocene or 
Oligocene) , at least 100 feet thick. 
( 4 ) Hard, calcareous marl, full of coral heads, with occasional 
indurated strata of white porous limestone of upper Oligocene age. 
These rocks are described as the Pepino formation and are exposed in 
the Pepino Hills north and northwest of Lares, 
(5) White, loose-textured limest ones composing the hills of the 
south coast, probably of Pleistocene age, although some of the lower 
strata may be as old as Oligocene. 
(6) Elevated reefs - these are poorly developed in Porto Rico. 
(7) Alluvial plains of Pleistocene age. 
The fossil corals obtained by Mr. Hill occur in the Pepino forma- 
tion, 4 miles west of Lares. They are of upper Oligocene age and are 
similar to the fauna of the Island of Antigua, 
List of fossil corals from Porto Rico . 
Astroccenia portoricensis Vaughan (also Antigua) 
Orbicella cav ernosa var. aatiguensis (Duncan) (also Antigua) 
Orbicella cavernosa Lin (also Antigua) 
Orbicella tenuis (Duncan) (also Antigua) 
■' Maeandra ? portoricensis Vaughan 
Siderascrea portoricensis Vaughan = ? S. conferta (Duncan) 
(from Antigua) 
Aga-ri-e-ia portoricensis Vaughan 
Astreopora portoricensis Vaughan 
Goniopora portoricensis Vaughan 
