Hi, It's good that you are enjoying your genealogical research and I hope that eventually you may come to enjoy learning about heraldry. I hope I can help you along.
Two very basic things before we start: Although it is of less importance, as you come to study heraldry in more depth you will find that a crest is the thing which sits on top of the helmet and is not in fact the coat of arms (it's a common misconception so don't worry). Secondly, and most importantly, there is actually no such thing as one coat of arms which belongs to all those named Morison. Generally in England (and Scotland) you can only claim a right to a coat of arms if you have been granted one for yourself or you have inherited one.
I was a bit confused when the heading of your post mentioned Morison Family Clan (Not Scotland Clan) because the arms you allude to are in fact Scottish but your genealogy refers to an English family. Incidentally, England doesn't have Clans and the concept is quite alien to the English and there is no such thing as Clan arms, only the arms of the Clan Chief. Anyway,there are quite a number of English families bearing arms but it seems that none of those have the saracens' heads you mention. The saracens' heads feature in a number of Scottish arms for various Morison families.
If you would like to know more about the English arms and their origins let me know.