Greetings,
The attached ammonite is from a locality of known Middle Bajocian (Middle Jurassic) age in British Columbia. It was found in direct association with professionally-identified specimens of Skirroceras, a subgenus of Stephanoceras. The diameter is about 30mm. I realize there is not much to go on here, since the venter is not exposed. It is involute, with dense, sharp ribs and a very narrow umbilicus.
Any thoughts?