The second the three Graptolites species that I've found in the Coburg formation is Dictyonema sp. It appears as a net like carbon coating on the rock face. Mostly you find them on small fragments of rock but occasionally you will get a big slab where you can get a feel for how big some of the colonies could get. Dictyonema is a genus that is extant from the Ordovician all the way thru to the Devonian but it is hard to get a species because most fossils are not preserved well enough.
On this sample, there is also some Melanostrophus sp. Graptolites.
Here is a link to the Baltic fossil ID website, FOSSIILID.info which has some more examples of this Graptolite.
Here are other examples of this Genus that I've collected in the Silurian aged Rochester shale, and Devonian aged Windom shale.
The Coburg formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
These fossils were collected from the St. Mary's Limestone Quarry in Bowmanville, Ontario. I used William Hessin's book "South Central Ontario Fossils", 2009, Self Published, pg. 130 to help identify these fossils.