I almost stepped on this one. Another P. syrtale, over 50 cm. The next pic shows them both. From the Middle Santonian, about 85mya. The first one I think is the male dimorph, with the stronger ornamentation, and the other larger, smoother one the female dimorph.
As you can see in this photo, only the "orange" part was exposed, the largest peice of rock that was covering the phragmocone is to the right. I didnt have a brush with me so I just wiped it of with my hand. Ants had built a nest under the other side so when I lifted it the other side was fairly clean (seen in the first post).
95% of the fossils in this formation are crushed or shattered so finding a good one is rare. On average there is a good fossil about every 2 miles along the outcrop.
I replaced this one as I had found it and covered it up a little, I will return to collect it later as a few museums here are after me to get them some nice fossils like these.
With the Fossils and History Forum being kinda slow lately, i think i'll post some old photos. I found this one back in '91, a large Placenticeras syrtale from the Mancos Shale. A B&W photo of it after preparation, and a picture of it in the museum at the local university (lower right).