9-Letter Words Matching ___S____A

There are 13 9-letter words that match ___S____A. 4 are common words, such as CONSORTIA and FORSYTHIA. A rarer one is PROSTOMIA. In this set, I is the most frequent open letter (10 words). 2 words contain a doubled letter.

Full list 13

consortiaforsythiaprosceniasubstratacausalgiahaustoriahoustoniatessiturabousoukiacrustaceahaustellaplasmodiaprostomia

About this list

Words
13 (4 common words)
Common example
consortia
Rare example
prostomia
Doubled letters
2
Ending in S
0
Most frequent letter
I (10)

Questions

How many 9-letter words matching ___s____a are there?

13. 4 of them are common words.

What is a common example?

CONSORTIA is among the common words in this set.