of American Geologists and Naturalists. 109 
The two lower formations are identified by their appropriate: fos- 
sils, which occur abundantly ; the Utica slate by its position and 
lithological characters; the Hudson river shales by the same 
characters, and by their upper member, which is an argillaceous 
limestone containing the stinted forms of Chetetes lycoperdon, 
which are usual in this the last period of the existence of the 
species. The red sandrock lies upon the last named rock in ac- 
tual contact, with a moderate easterly dip. The upper part of 
this section is repeated in the line of the strike in several other 
* localities, but one only, Buck mountain, three miles north, has 
sufficient elevation and steepness to exhibit the lower part of the 
series. 
_ The assertion which had been made, that there is a line of 
fracture high up the side of the mountain, above the Trenton 
limestone, was shown to be entirely unsupported by any facts. 
Not only is there no evidence that sucha line of fracture has 
brought up the shales from beneath the Trenton limestone, the 
sils in the upper member of the shales prove that the present 
is their original relative position. But these shales are the 
Taconic slates of the Taconic system. . 
_ From position, therefore, it is inferred that the red sandrock is 
More recent than any of the Champlain Division. Its fossils af- 
ford less demonstrative evidence. With the exception of F'uc 
ley are rare, having been found only at Highgate, where frag- 
ments of the shields of trilobites, having some resemblance to 
Conocephalus, occur very abundantly, and Atrypa hemispherica (?) 
very rarely. ‘These fossils, especially the latter, if correctly iden- 
tified, indicate the period of the Medina sandstone and Clinton 
group, regarding these two rocks as belonging to one period 
it was j 
Taconic q ) 
above named red sandrock. In this section there is a gradual 
change in the lithological characters from the red sandrock to the 
quartz rock ; the difference in the lithological characters, how- 
rocks. But since a small part of the section, on the opposite 
sides of which the change of characters is most conspicuous, is 
concealed by drift, the identity of the Taconie quartz rock with 
the Medina sandstone was not positively affi . 
_ A section from Buck Mountain through Waltham into New 
Haven was exhibited, which rendered it somewhat probable that 
the Stockbridge limestone of the Taconic system is the equiva- 
lent of the calcareous rocks which overlie the red sandrock, 
 Tather than of the lower limestones of the Champlain Division, 
as has been commonly supposed. 
