Is the final "a" in words like clárseacha pronounced as "ee" in most Irish dialects, or is this a pronunciation peculiar to Cois Fhairrige? Thanks!

No, the a would be a dull 'ah' sound called a schwa. It might be an old dative singular form, like 'clársigh', used instead of the old nominative, but someone who knows better will fill you in

Coincidentally, I was about to start a thread about something like this. How come I've heard "ceisteanna" and "fuinneoga" pronounced as "ceisteannaí" and "fuinneogaí"? Is it dialectal, or has it something to do with case?

Your examples I'd say are down to modern Irish promiscuity with plural endings and/or using aí generally as an ending. We could be seeing old dative pls with aí, plural aí, and dat sing as ach -->igh all been collapsed to one form as they are now just singular or plural forms

It is dialectal. In Connemara and Ulster, -(e)anna is -(e)annaí and -(e)acha is sometimes -(e)achaí. I don’t think it’s an old dative, it’s just a double plural mark: -anna + -aí.

^ Aontaím, it's not ALWAYS the case.. Another common example i hear is seachtainí..

But "seachtainí" is the plural of "seachtaine". . . ?

Aontaím, it's not ALWAYS the case.. Another common example i hear is seachtainí..

Sorry but I don't see the connection between this and what we said...

Yeah, it's dialectal, just a different way of pronouncing the plural forms. Technically, yes is should be pronounces "-acha" or "-anna", but it is quite common to hear "-achaí" or "-annaí".

-annaí and -achaí have arisen from plural datives, as -annaibh and -achaibh were pronunced like annaí and achaí all along in Connacht and Ulster.

seachtainí is just a plural of seachtain. It is not related to the issue above.

-annaí and -achaí have arisen from plural datives, as -annaibh and -achaibh were pronunced like annaí and achaí all along in Connacht and Ulster.

Could you tell us what are your sources about that?

Rahilly and the article called "On the history of noun declension in Irish" which published in one Russian Celtology journal. If you are interested and can read in Russian - I will find precise bibliography for you. The article entertains history of all "strong" plural forms.

Seo dhuit:

The book:
Академия Наук СССР
Институт языкознания

Кельты и кельтские языки

Из: Наука, Москва 1974


The article:
А. А. Королёв - Некоторые вопросы истории ирландского именного склонения - pages 84-94

Thanks. I only know Basic Russian, not enough to read the article.

However, the dative plural ending is pronounced [əβ´] in Ulster, or sometimes [u].

N. Williams wrote this in Stair na Gaeilge (p.451, §3.5):

"Ní dócha go bhfuil mórán baint ag an bhfoirceann -(a)ibh féin le -(a)í sa chuid is mó den tír, áfach."

Cé aige atá an ceart?

Rahilly had other opinion. This is what he says on page 78:

"In northern Irish -ibh has three pronunciations -i, -iv and -ú. In most of Connacht (including the northern parts of Galway) -ibh is pronounced -í, just as -igh is [...] The same pronunciation of -ibh was probably known in Ulster also. The strong tendency which exists throughout Northern Irish to affix -í to the plurals of nouns (e.g. daoiní, piantaí, putógaí, cailleachaí, ceisteannaí) is due, not only to the existence of the frequent plural termination -í (<-adha) but also, very probably, in part to pronouncing the -ibh of the old dative plural as í". The there is a footnote - "Tadhg Ó Neachtain frequently writes the termination -ibh (which he doubtless pronounced -í) in the nom. and acc. pl.)

To support Rahilly's point and refute statement in Stair na Gaelainne - I would remind that although -igh is pronounced as [ig`] as a rule in Munster, there many standard situations where it is not pronounced at all, e.g. in family names (Ó Dála(igh), Ó Luinsi(gh)), in words where there is no alternation [g`]:[-] - is dó(igh) liom, easpa(igh), iomarca(igh), Trá(igh) Lí, Ma(igh) Eo, Fionn Trá(igh).

Thus, it is quite probable that -ibh when existed in Ulster it was treated quite differently from any -ibh where -bh is a part of the stem.