What is the formal name for this fallacy?

Question

It's been 47 years since I studied formal logic, and I cannot seem to find a textbook that approaches it in just the same way. We started with the classic A, I, E, and O propositions, and analyzed syllogisms. For example, the most basic syllogism is MaP, SaM, SaP. (All cats have tails, Tabby is a cat, therefor Tabby has a tail.) What is the proper name for the fallacy MaP, SaP, SaM? (All cats have tails, Tabby has a tail, therefor Tabby is a cat.

Answer 1

Yes, the syllogism commits the fallacy of undistributed middle.

All cats are animals that have tails.

All animals identical to Tabby are animals that have tails.

So, All animals identical to Tabby are cats.

The form is AAA-2. The middle term is 'animals that have tails', and it is not distributed in either occurrence.

Answer 2

If I remember correctly, it is the Fallacy of The Undistributed Middle Term.

Answer 3

It is the undistributed middle, see source

Answer 4

I've seen this called the fallacy of affirming the consequent.  I've also seen it called "The Converse Error"