34 



Keport of the State Geologist. 



appears in the more arenaceous strata. But this alternation concerns only the 

 upper portion of these beds. To this series of strata representing the 

 prolonged existence of the Naples fauna the term Wiscoy shales and sands has 

 been applied. In protracting, upon the evidence of the contained fossils, the 

 scope of the Portage group to include these beds, we shall not appear to 

 violate propriety for they did not escape the observation of Professor 

 Hall, who at the close of his description of the Portage group says 

 (1843, p. 248) : "The Portage sandstone is succeeded by olive shaly sandstone 

 and shale and this by black micaceous slaty shale with septaria ; to this follow 

 shales and coarse sandstones with fossils of the Chemung group." Their 

 position is illustrated in the section along the Genesee valley from Portage 

 southward, given on plate xi of the work cited. 



The fauna of the typical section of the entire Portage series along the 

 Genesee valley, is the fauna of Manticoceras intumescens. Not alone does this 

 species here appear, become profuse in individual development and varietal 

 expression, culminate and decline, but its associates are of a peculiar sort 

 which likewise, for the most part, here appear, flourish and depart. Such 

 are other forms of the genus Manticoceras, species of Gephyroceras, Belo- 

 ceras, Probeloceras, Tornoceras, JBactrites, Clymenia, numerous forms . of 

 BucJiiola, "Cardiola" and other genera of Cardioconchs, and the " Lunu- 

 licardiums," Chmwcardiola, Pinnopsis, Pterochaenia, Honeoyia, as well as a 

 few specific forms of gasteropods. No less characteristic is the dearth of 

 brachiopods. 



Through the early part of the period this is the fauna of all the sedi- 

 ments, shales, calcareous layers and nodules, and sandstones wherever the 

 last are found to bear fossils; through its latest phases it is distinctively the 

 fauna of the shales and not of the sandstones, but it is then that the fauna was 

 retreating and readvancing, with the appearance and temporary withdrawal 

 of the Chemung fauna about to prevail. In following the Portage series in 

 its entirety to the east through Yates, Schuyler, Tompkins and into Cortland 

 and Chenango counties, we find that its western fauna is gradually and wholly 

 replaced in the rock series. Species of the genera above mentioned rapidly 

 disappear and their places are taken by strangers to the western sections, 

 especially by brachiopods and lamellibranchs similar to those occurring in the 

 Hamilton fauna below, so that through Tompkins county and in the meridian 

 of Ithaca we encounter a commixed association, the interleaved edges of the 

 two adjacent faunas of the Avest and central areas. Where the strain of the 

 eastern fauna is the purest, as in Cortland and Chenango counties ; where it 



