Yes, FORNICES is a Scrabble word!

Letter values in Scrabble US: F 4, O 1, R 1, N 1, I 1, C 3, E 1, S 1.

Is it a valid word?

FORNICES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

generally any arch shaped structure (but often it refers to the arched roof of an anatomical space)
an arched bundle of white fibers at the base of the brain by which the hippocampus of each hemisphere projects to the contralateral hippocampus and to the thalamus and mamillary bodies

Also: trigonum cerebrale.