Catalog Number: CG-0046
This week I found a third Solenochilus, this one with a still attached lateral spine. Solenochilus has a unique feature in a pair of lateral spines that were assumed to be used to help the creature swim in a stabilized nature. In numerous specimen photos I’ve seen, I have not seen many with spines still attached. Like most features of a shell that are fragile, these are likely to break off after death or in removing the specimen from the matrix.
I originally thought this was a Metacoceras, as it was roundish. The top of the shell was exposed to a local stream, and it was eroded and smoothed. There is a hole in the top, but it is off-center and small. It turned out that a sea pen shell had penetrated through the top of the shell. There is another on the bottom, however in my opinion they don’t exactly match up, but it’s possible.
I spent a great deal of time trying to free the spine, having to hammer through a fossil clam that was right on top of it. Eventually I got close, however a tip broke off. This is fortunatate though, as I believe I have revealed a spine steinkern.
Page K440 of the Treatise of Invertebrate Paleontology Volume K has a beautiful illustration of Solenochilus springeri, showing well defined spines.
With spine pointing down. 
Underside of specimen. Another probably sea pen fossil in the middle.
