When ds was born he had very noticable gaps in his skull, radiating from his fontanelle, which is of course normal. It seemed to get less obvious, however one side has recently become more noticable (he is 6 months) Too look at it just looks like a visible vein, until you feel it or look from an angle.
I think you can see it on the photo in the gallery on my profile. I cannot remember at all when the bones in their heads are supposed to close up (third time mum - seem to have forgotten everything). Not worried, just curious.