Graptolites are extinct animals that lived in floating colonies during the early Paleozoic. This is a Dictyonema retiforme from the Rochester Shale near Middleport, NY which dates to the Silurian period. The preservation is not the best but it is a good example of the dendritic growth habit commonly found in post Ordovician genera.
There is also an unknown, Strophomenid(?) type brachiopod on this plate.