Plant vs Molusk (or neither!)

[John.E.K]

Found this rock in Charmouth beach (south west coast of England) a few months ago. The period is early Jurassic and is generally dated to ~190m years ago. 

 

I gave it a friend and have got into a debate as to whether it is a fossilised plant or part of a mollusk. Can anyone help resolve this argument/confirm that I am right?!

 

Thanks,

J

[Rockwood]

Belemnite 

[Fossildude19]

Looks like a broken belemnite. 

[John.E.K]

Cheers chaps- that was quick and fairly unanimous!

 

I disregarded belemnites previously as I couldn’t see any examples of a forked fossil...is this due to damage or is my knowledge lacking?(Probably the latter)

[Rockwood]

It's sectioned nearly down the midline showing the opening in the end of the guard. The correct terminology escapes me at the moment.

[TqB]

16 minutes ago, Rockwood said:

It's sectioned nearly down the midline showing the opening in the end of the guard. The correct terminology escapes me at the moment.

Alveolus, which holds the phragmocone (missing there, as commonly the case - the alveolus is filled with sediment).