1895. | NEW YORK ACADEMY OF SCIENCES. 21 
affording a section of the dike several feet east of that figured 
by Kemp. The fissure appears to have split so that now we see 
a double dike made up in section of two wedges, the lower of 
which is inverted. 
Port Kent and Ausable Chasm were next visited. Back of 
Port Kent is an extensive plateau made up of thick deposits of 
sand and gravel. Underlying this terrace formation is the 
Potsdam sandstone. This is in layers varying in thickness 
from one to several feet, lying nearly horizontal It isa hard, 
compact quartzite, well resisting weathering except along the 
deposition planes. It is everywhere much traversed by vertical 
joint planes. Thus the loose bedding and the vertical jointing 
enable the stream to easily undermine the high banks. The 
larger part of the erosion is probably of this kind; there being 
apparently a small amount of abrasion. A few faults cross the 
chasm causing deep fissures in the opposite walls. The stream 
seems often to follow the line of a fault and then to turn abruptly 
aside, following the course of one of the joint systems. 
At Plattsburgh the writers were joined by Professor H. P. 
Cushing, of Cleveland, Ohio, who very kindly devoted several 
days to pointing out the best localities in the vicinity of Platts- 
burgh and Chazy. At Bluff Point and along the shore south of 
Plattsburgh good sections of the Chazy rocks were examined 
and good collections of fossils obtained. Of special interest is 
the discovery of Foraminiferal shells in microsections of Cal- 
ciferous limestone from south of Plattsburgh. The minute shells 
resemble somewhat in general shape those of the genus Lima- 
cina among the Pteropods. Crab Island, off Bluff Point, is an 
excellent collecting ground for Trenton fossils. The island has 
probably received its name from the numerous specimens of 
trilobites of the genus Asaphus which may be found in the loose 
blocks on the shore, which fossils are generally believed to be 
crabs by the natives. 
Beekmantown, four miles north of Plattsburgh, is where the 
beautiful specimens of Ophileta complanata were collected by 
Prof. Seely, and which were described by Prof. Whitfield in 
Bull. Amer. Mus. Nat. Hist. II., 48; Pl. vir. These gastropod 
shells occur in vast numbers in a calcareous sandstone that out- 
crops in a low ledge one hundred feet wide, extending for some 
distance through the fields. 
Cumberland Head, a few miles northeast of Plattsburgh, fur- 
nishes many outcrops of a black, shaly limestone. It contains 
a trilobitic fauna not found at any other point along the lake. 
The contained species are not forms that have been hitherto 
noted in New York, but resemble certain ones described by 
Billings from the Quebec group of Newfoundland. 
