Grave stones

I was in St Andrews church in Hatfield Peverel, today, a beautiful old church about 20 minutes from Chelmsford where I came across these, to me, unusual gravestones.
They appear to be body shaped and some have name markers at both the head and the foot which made them even more so. Those I could read seemed to date from the early 19th century. I couldn't find anything locally about them but will look elsewhere.