Manlius Limestone Group
In New York (and Ontario, Canada), the Manlius Group appears to be equivalent to most of the "Helderberg" Group of Eastern New York. In the Syracuse Region, Erieopterus microphthalmus marks the beginning of Early Devonian sedimentation. Within this region, Erieopterus occurs within the upper portions of the Chrysler Formation, but more importantly, from the bottom to the top of the type Olney Formation. The photos below show the author, Samuel J. Ciurca, Jr., studying the fantastic ex- posures of the Olney Limestone at the type locality (circa 1980). Erieopterus appears in countless numbers within this formation.  Photos by Claudio Gambacorta, Rochester, New York.
The Manlius Group consists of sev- eral formations, clearly defined by lithology.  Named after the town of Manlius, in Upstate New York, the Manlius Group contains a fauna consisting brachiopods, ostracods, pelecypods, some corals and two important elements: stromatolites and stromatoporoids.
   Intercalated eurypterid-bearing units are notable and indicate the first appearance of the Devonian eurypterid faunas in the sequence. Below this are Late Silurian, euryp- terid-bearing sequences.
ABOVE: The author studying and measuring part of the Olney Limestone.  The rock consists, mostly, of very resistant limestone ("ribbon limestone") and thin intervals bearing the Erieopterus Fauna.  At the base, stromatolites initiate the sequence and the first appearance of Erieopterus occurs here.  The middle Olney Limestone is more marine - several brachiopod species appear and crinoidal debris is quite evident.  Toward the top, the cycle is reversed - and Erieopterus reappears below a thick layer of mudcracks.  Overlying the Olney Limestone are waterlimes and mudcracked beds (Elmwood Forma- tion), the thin Clark Reservation Formation, and other units.  No eurypterid remains have ever been found in the upper portions of the Manlius Group, ie. above the Olney Limestone.