1891.] 
335 
[Hyat. 
epoch, which extend on the St. Lawrence to the mouth of Lake 
Ontario, on the Ottawa to a considerable disance above the city 
of Ottawa, and along the whole length of Lake Champlain. He 
exhibited a map colored to show the area thus occupied by the 
sea immediately after the departure of the ice-sheet. On this 
map a narrow strait of the sea was represented as extending 
from the ocean at New York northward along the Hudson and 
Lake Champlain to the broader bay which then stretched far in- 
land from the Gulf of St. Lawrence. 
Baron de Geer believed that the Catskill delta was formed at 
a time when New England and the contiguous portion of Canada 
were made an island by this strait on the west and the enlarged 
gulf on the north. 
Mr. Warren Upham attributed the Catskill delta to deposition 4 
in a glacial lake bounded on the north by the barrier of the ice- 
sheet during its retreat from the basin of Lake Champlain and 
the St. Lawrence valley. The barrier of this lake on the south 
was thought to have been land beyond the present mouth of the 
Hudson, which afterward sank beneath the sea level. The 
subsidence of this coast is still going on ; and the submerged 
channel of the Hudson has been mapped by the U. S. Coast 
Survey. The absence of marine fossils from the post-glacial 
beds of the Hudson River valley was cited as evidence that this 
valley has not been occupied by the sea, either as an estuary or 
strait, since the Ice age. 
December 2 , 1891 . 
Vice- President W. H. Niles in the chair. Thirty-two persons 
present. 
The death of the Society’s former Secretary and Librarian, 
Mr. Samuel Dexter, was announced. 
The following paper was read : 
REMARKS ON THE PINNIDAE. 
BY ALPHEUS HYATT. 
The paper of which the following is an abstract arose from an 
effort to follow out the phylogeny of the group for the purpose 
