148 Transactions. 
metamorphism than the diorites, for they are very commonly gneissic. 
More basic facies are found as ophitic rocks which structurally an 
mineralogically approach dolerites and epidiorites. The variety of feldspar 
that they contain is, however, seldom more calcic than andesine-labradorite, 
and is usually basic andesine, so that the writer's earlier designation 
of such rocks as dolerites is objectionable in spite of the dominance 
of ferro-magnesian mineral over plagioclase. It does not appear con- 
With them may also be included a few less basic rocks which have a 
structure approaching the trachytic. They are fairly coarse and non- 
porphyritic, and are built of dominant plagioclase in large irregularly 
disposed laths accompanied by uralite. 
to attempt reclassification in the absence of exact knowledge of their 
chemical characters. 
Rhyolitic material of rather felsitic nature is the main igneous con- 
stituent of some bands of finer conglomerate near Riverhead, but it is 
particularly scarce elsewhere, and only one specimen was collected from 
northern occurrences. It proved to be a type with phenocrysts of acid 
plagioclase and a little biotite surrounded by an abundance of turbid 
rather glassy base. 
