PRIMORDIAL FAUNA AND POINT LEVI FOSSILS. 289 
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In this table we find, of previously recognized trilobites of the 
primordial fauna, two genera and five species; of previously known 
genera of the second and third faune, four genera and eight species ; 
two genera before known in the Potsdam sandstone and seven species , 
and of Agnostus, which is of the first and second faunze, two species; 
and one new genus with nine species. 
These are certainly very curious results ; and a modification of our 
views is still’ required to allow four genera and eight species, (or 
leaving out Amphion) three genera and six species of the Trilobites 
of the second fauna to be associated with two genera and five species 
of Trilobites of the primordial fauna, and yet regard the rocks as of 
primordial origin. 
The Brachiopodous genera, Lingula, Discina, Orthis, Lepteena, and 
Strophomena, have a great vertical range, and are known in the 
Lower and Upper Silurian, and most of them in the Devonian ; while 
Camerella so far as known is a Lower Silurian form of the second 
fauna, (perhaps also in a lower position). 
Of the Gasteropoda, Maclurea and Ophileta are restricted to 
Lower Silurian rocks, but occur mainly in the second fauna. The 
other genera occur likewise in the second fauna and in the Upper 
Silurian rocks, as well as some of them in Devonian. The same is 
true of the Cephalopoda enumerated. 
Tetradium is known in the second fauna of the lower Silurian 
rocks, and in the upper part of the Hudson River group at the west. 
Dictyonema is a genus known from Lower Silurian to Devonian strata. 
Graptolithus proper extends to the Clinton group of New York; 
and the same is true of Reteograptus. Thamnograptus occurs in the 
rocks of the Hudson River group near Albany, and in the Quebec 
rocks. Phyllograptus and Retiolites are known in the Quebec rocks 
