‘ ; ‘ 
over the New Haven Region. 343 
Some of these points were discussed by me in 1870, in a 
paper on “the Geology of the New Haven Region,” published 
of Mr. R. M. Bache, assistant U. S. Coast Survey, laying down 
the features of the surface with great accuracy, and indicating 
the level over the whole area by 20-foot contour lines. IA my 
bridge and Bethany. ; 
The western border region has a rather abrupt eastern front, 
and rises in height from 100 feet above mean-tide level on the 
south to 650 feet on the north. This western border was the 
Western margin of the deep Connecticut trough and estuary of 
Triassico-Jurassic time, all the rocks of the region eastward 
Periods. South of Westville it is a double ridge—that of a 
broken-backed anticlinal—a shallow valley of ledges and 
region—West River, Mill River and the Quinnipiac—open 
tock Ridge” of trap (doleryte) 400 to 600 feet in height, 
together with the various the este hills that lie to the east of it. 
* The valley is called (from one portion of it at M on the map) Maltby Park 
Valley. See also the map on page 358. 
