62 Jj. W. DAWSON ON PALHOZOIC FOssits 
sited that it could take part in the mineralization of marine organic 
remains. 
The condition of the fragments of Silurian fossils in the limestones 
associated with the nacreous or hydro-mica slates is of interest in 
connexion with this subject. The shining laminated mineral asso- 
ciated with these fossils has been regarded from its chemical com- 
position as a hydro-mica. Under the microscope, however, it shows 
a want of homogeneity which suggests the presence of two or more 
silicates, or the association of crystals of hydrous mica with minute 
grains of siliceous matter of some other kind. Though now highly 
crystalline, it must originally have been a fine sediment, since it fills 
the finest cells of Stenopora and Péilodictya. Nor can its present 
state have been produced by any extreme metamorphism, as the 
undistorted state of these fossils amply testifies. Further it is in- 
teresting to observe that though the hydrous silicate is little mag- 
nesian, the fossils themselves are not infrequently converted into 
dolomite. In these fossiliferous beds there are also tabular crystals, 
apparently of anhydrous mica, little groups of crystals of tremolite, 
cavities filled with quartz, and crystalline grains of a mineral having 
the microscopical characters of olivine; and these have been de- 
veloped or included in the mass without injury to the structures of 
the most delicate corals. 
Similar appearances are presented by limestones from other parts 
of the Quebec group, of which a great series of slices has been pre- 
pared by Mr. Weston under the direction of the late Sir W. HE. Logan, 
who, in his later researches in this group of rocks, gave much atten- 
tion to the microscopic fossils in the more altered beds, as a means 
- of determining their ages. Besides large series from Melbourne and 
its neighbourhood, I have examined slices from Stanford, Farnham, 
Cleveland, Bedford, Orford, Arthabaska, Point Levi, Riviére du Loup, 
and other places, in most of which Lower Silurian fossils occur as- 
sociated with hydrous silicates. 
The fossils above referred to occur in rocks undoubtedly of Lower 
Silurian age, and regarded as altered or metamorphosed members of 
the Quebec group. In the unaltered representatives of these rocks 
at Point Levi and the island of Orleans there occur considerable 
quantities of a true glauconite, which has been analyzed by Dr. Hunt, 
and which is without doubt an original deposit in the sandy and 
argillaceous beds in which it occurs, which in many cases are pre- 
cisely similar to Cretaceous greensands. Dr. Hunt’s analysis shows 
that this glauconite contains alumina, iron, potash, and magnesia, 
and thus approaches to the Laurentian loganite. In the forms of 
its little concretions it resembles the serpentine grains in the 
Laurentian limestones; and like modern glauconite it has moulded 
itself in organic forms. Some of these are spiral or multilobate, as 
if casts of minute univalve shells or of spiral and textularine Fora- 
minifera*, Others are annular or are arcs of circles, and some pre- 
* Ehrenberg has found casts of rotaline and textularine Foraminifera in 
Lower Silurian beds in Russia; and such forms occur in Upper Silurian lime- 
stones in Nova Scotia, 
