JEFFERSON COUNTY. 
405 
in. 
1. Cypricardites angustifrons. 2. Cypricardites ovata. 
The preceding figures are offered as an illustration of the palaeontology of the Champlain 
group. I have been able to furnish the most important of all the sedimentary rocks of the 
Second district, the principal motive having been to give accurate drawings, by means of 
which comparisons could be made with the fossils of other rocks in otlier portions of the State 
and country. I have not deemed it so necessary, in this place, to settle and clear up all doubts 
as it regarded identity of species, as to obtain good figures for comparison. I have therefore 
omitted the specific names in several instances, considering these as of little consequence in 
comparison with the determination of the position and range of the fossils themselves. 
In this connection, I may remark farther, that it will be seen from the preceding figures, 
that all the sedimentary rocks of the Second district are fossiliferous, and that the lines of de- 
markation between the rocks are very strongly defined by the fossils alone. To the practised 
eye, very little difficulty is experienced in distinguishing the rocks by means of their litho¬ 
logical characters ; but it is only by means of the fossils, represented truly in drawings, that 
correct comparisons can be made abroad. These enable the geologist to institute at once 
those comparisons which are necessary to establish identities or differences between rocks at 
a distance. Though a minute detail be given of the lithological characters of a group, still 
it is impossible to present it as it is ; but when an accurate figure is given of an imbedded 
organic body, there is furnished at once as it were a living character, one that is far more 
constant than even the mineral character of the group or rock itself. 
I 
