Dropped "D"s and "T"s

When people poke fun at the Boston/Rhode Island family of accents, the "conservation of rs" problem gets a lot of attention (cah vs. car: non-rhoticity and idear vs. idea: intrusive R). Undoubtedly, this is one of the most easily recognizable linguistic quirks of the region.

A subtler characteristic of southern New England speech is the routine dropping of ds and ts. I have no idea what this is called, but it seems that speakers of other American accents have a similar habit. Dropping ts and ds is much more common than full-blown non-rhoticity.

Why do I care? Gravestones, of course:

Hugh Ellis, Newport, RI (1723)

"Granson"

Samuel Winsor, Providence, RI (1758)

"Baptis"

also, potentially, "Winsor"

I don't know how other people pronounce this, but I would pronounce "Windsor" as "Winzzer," as in "South Winzzer, Connecticut." Was he Samuel "Windsor" or "Winsor"? This book says "Windsor."

Susannah Lane, Billerica, MA (1713)

"Augus"

These may be coincidences, but I'll be on the lookout for more d/t irregularities from now on.