Found this picture in this latin book. It seems to distinguish between a tarha and a tarha aharona. Any ideas what it is?
R' Zalman of Hanau writes (Shaare Zimra, gate 2, paragraph 5):
There are other helper accents that are not so common in Scripture but appear occasionally and are listed in the Mesorah. They are yareach ben yomo, mer'cha ch'fula, and m'ay'la.
He then describes the first two of those and then, in paragraph 7, continues:
M'ay'la looks like a tip'cha [=tarcha]. It's found in five places on a word that has a sof pasuk and in ten places on a word that has an esnachta, in the location for a meseg. It's also found in eighteen places before a zarka, but then it looks like a mer'cha and in a separate word.
He goes on to list, from the Mesorah, where these appear. Those in the Pentateuch are Gen. 8:18 "וַיֵּ֖צֵא־נֹ֑חַ", Lev. 21:4 "לְהֵ֖חַלּֽוֹ", Numbers 15:21 "לְדֹרֹ֖תֵיכֶֽם", and Numbers 28:26 "בְּשָׁבֻעֹ֖תֵיכֶ֑ם".
I'm guessing that that's what your book is referring to when it lists tarcha acharona among the helper accents, since the m'ay'la (a) is a helper accent, (b) looks like a tip'cha (=tarcha), and (c) is in some sense acharona (last), specifically in that it is on the last word of the (half-)pasuk.