592 PROCEEDINGS OF THE ACADEMY OF [NoV., 



agglomerate is in excess of the material in the form of flows. Many 

 of the tuffs and other materials have midergone alteration, and, 

 according to the statements of Mr. Tempany, metamorphosed 

 sediments occur. Such is the Seaforth limestone as described by 

 Spencer, but specimens of this rock which I was shown in collections 

 do not show metamorphism to any considerable extent. Water- 

 deposited tuff may occur, at least near the borders of this formation, 

 and in the tuffs of the Central Plain area I saw deposits not greatly 

 different from those observed in these igneous foundation rocks of 

 the island. No definite volcanic cone from which these deposits 

 came is now in existence, all the hills being much eroded and dis- 

 sected. Remnants of such cones may exist near Five Islands Bay, 

 or the bay itself may represent the site of a crater. Another remnant 

 of a crater was reported as being in existence near the southwest 

 corner of the island, but no cone exists there at present. 



2. The Seaforth Limestone. 



I did not visit the type locality of this material, and only had the 

 opportunity of inspecting two lots of specimens from the formation. 

 Spencer describes it as ''occurring at a few points in the valleys of the 

 mountain zone" or among the rocks of the igneous basement; and 

 states that it is a compact dark gray limestone. Mr. Tempany gave 

 a similar description of its appearance and occurrence, but the 

 specimen of it which he showed me in his collection was a somewhat 

 flinty rock with undoubted Orbitoides in it. Mr. Gillie, rector of the 

 parish of St. Mary's, who resides near the southwest corner of the 

 island, showed me some pieces of a limestone from Seaforth of quite 

 a different character. It was a dark gray compact limestone, but 

 crowded with the shells of bivalves, probably oysters, that were 

 specifically undeterminable. There was nothing in either of these 

 specimens to lead me to suppose that they were older than Oligocene, 

 while the occurrence of the Orbitoides, in a form not greatly different 

 from that found in the white limestone, rather pointed to this age 

 for the deposit. Purves did not recognize this Seaforth limestone. 



3. Water-deposited Tuffs and Shales, with included Marls 

 AND Cherts. 



These formations occupy almost the entire area of the Central 

 Plain. They include the divisions recognized by Purves under the 

 names B, Lower stratified tuffs; C, Lower limestone and marine 

 chert; D, Volcanic sands and sandstones; E, Lacustrine and fresh- 



