No. 50.] 
Fossils are rare in the lower part of the Frankfort slate, but are nu- 
merous at the upper part where it joins the next series, the Pulaski 
shales. To which of these two masses they belong, or if they form a 
separate mass, has not been determined ; but that they form an impor- 
tant geological line of division is certain, for there is no essential differ- 
ence between the fossils, whether seen at the mill race at Lee centre, 
or Whitall's quarry, near Rome, Halleck's springs, in Hampton, or the 
gully near Utica and the Cohoes, near Waterford. In all these locali- 
ties, the characteristic shells of the Pulaski shales are wanting, and 
others appear, that had no previous existence in the district. Among 
the Fossils are cryptolithus, probably the tessellatus Pentacrinites 
— ■ and Trimerus . 
Halleck's spring was commenced in the upper part of this rock, and 
it is not improbable that the springs of Ballston, Saratoga and Albany 
may be in the same rock, (the Frankfort slate,) and for these reasons. 
The fossils of Waterford show the existence of the upper part of the 
mass on the Hudson. Secondly, that there are extensive and thick 
masses of argillaceous rock upon that river, whose age is matter of 
controversy. Thirdly, that organic life abounded in the period of the 
Trenton limestone, and disappeared in the lower part of the Black slate, 
reappearing only at the upper part of the Frankfort slate, leaving a 
thickness of mud rock, of at least 400 feet, comparatively destitute of or- 
ganic bodies. Now what cause so well explains this absence of life, 
as the existence of saline matter, as to kind or quantity, unfavorable to 
its existence or development. 
Pulaski shales. Called in the last report the shales of Salmon river, 
which we have changed to the first name, from finding them at the vil- 
lage of Pulaski, imaccompanied by any other mass. There the argilla- 
ceous part predominates at the lower part of the village, accompanied 
by some carbonate of lime, whilst above the village we find the sand- 
stone begins to predominate. 
The fossil which best characterise these shales are Pterinia carinata 
and Cyrtolites ornatus. Besides there are others whose individuals 
are very numerous, as Pterinia planulata, P. Modiolaris, P. pholadis 
and Delthyris equistriata and others not yet named. Again those which 
are common to the Trenton series, such as Strophomena alternata, Or- 
this testudinaria, Bellerophon apertus, Calymene blumenljachii. 
