I think I have identified the Fine Grin, or Tribe of the Land and the Fine Erluma, or Tribe of the Saint.
It looks as though the Dál nAraide (Fiacha Araidhe) is of the tribe of the saint and Dál Riata (Fiach Fearmara) is the tribe of the king.
I keep going back to this as the coarbs, according to the laws of the time, had to come from one of these two tribes – if at all possible. In the absence of any evidence to the contrary this has to be a sound starting point.
The Ulaid tribes
The main Ulaid tribes were the Ui Echach Coba, the Dál nAraide , and the Dál Fiatach. Lesser kingdoms within the reduced Ulster were the Conaille Muirthemne and the Dál Riata or Dál Riada.
John Francis Byrne, in his Irish Kings and High-Kings, says at page 107:
"The polity of Ulaid was somewhat peculiar, in that the over-kingship was not confined to one dominant dynasty, but was shared between those of the Dal Fiatach in eastern Down, the Dal nAraidi of Antrim and the Ui Echach Cobo of western Down. The position of the Dal Riata in the Glens of Antrim, whose kings resided in their Argyllshire colony, was also anomalous, as was, to a lesser extent, that of the border state of Conailli Muirtheimne in Louth."
"The dynasty of Dal nAraidi, whose kings resided at Raith Mor east of Antrim town in the district known as Mag Line, emerged as the dominant group among the Cruthin, although the Ui Echach Cobo (in the baronies of Iveagh, County Down) also supplied some over-kings of Ulaid." Byrne, page 108.
U553.1 "Death of Eochu son of Conlaed i.e. king of Ulaid, in whom the Uí Echach Ulad originate."
The Dál nAraidi and their sub branch the Ui Echach Cobo were Cruithni and sometimes referred to as Irish Picts.
Descendants of Fiach Fearmara – The Tribe of The King
Several sources state that both Loarn mac Erc and Donn Sleibe Mac Eochada descend from Fiach Fearmara
In Irish Pedigrees – The Stem of the Dunlevy family, Princes of Ulidia, it says Tuirmach Teamrach, the 81st Monarch of Ireland had a son named Fiach Fearmara, who was ancestor of the Kings of Argyle and Dalriada, in Scotland: this Fiach was also the ancestor of MacDunshleibe and O’Dunsleibhe, anglicised Dunlevy, Dunlief, Dunlop, Levingstone and Livingstone. ….According to Dr O’Donovan descendents of this family (Cu-Uladh the son the last MacDunshleibe King of Ulidia), soon after the English invasion of Ireland, passed into Scotland, where they changed their name.
From the Genelach .H. Dhuinn Slebhe from O'Clery's Book of Genealogies: “1789. Cu uladh m Concobair m Duinn slebe (o ffuilit .h. Duinn slebhe) m. Eochada m Neill m Eachdach m Ardgair m Madadain m Aedha m Eochugain m Aedha m Eachdach m Fiachna m Aedha roin m Beicc boirche m Blaithmaic m Mail coba m Fiachna m Demain m Cairill m Muiredaigh muindeirg m Forga m Dallain m Dubhtaigh m Mianaigh m Lughdhach m Aenghusa finn m Ferghusa duibhdhetaigh m Iomchadha m Fionncadha m Ogamain m Fiatach finn (o ra dal tFiatach) m Daire m Dluthaigh m Deithsin m Eachadach m Sin m Rosin m Trein m Roitrein m Airndil m Maine m Forga m Feardaigh m Oilealla erann m Fiacha fer mara m Aonghusa turmigh m Echach foiltletain m Oilella caisfhiaclaigh m Connla cruaidcelgaigh m Irereo gleofhataigh m Melge molbthaigh m Cobthaigh caoilbregh m Ughaine moir.”
“So for instance when after 1137 the Dal Fiatach kingship was confined to the descendants of Donn Sleibe Mac Eochada (slain in 1091), the rigdamnai set themselves apart from the rest of the family by using the name Mac Duinnshleibhe (Donleavy)." Byrne, page 128
The Book of Ballymote provides this early list of Irish kings of Dal Riada: Aengus Turmech (of Tara), Fiachu Fer-mara, Ailill Erand, Feradach, Forgo, Maine, Arnail, Ro-Thrir, Trir, Ro-Sin, Sin, Dedad, Iar, Ailill, Eogan, Eterscel, Conaire Mor, Daire Dornmor, Coirpre Crom-chend, Mug-lama, Conaire Coem, Coirpre Riata (Cairbre Rioghfhoda), Cindtai, Guaire, Cince, Fedlimid Lamdoit, Fiachu Tathmael, Eochaid Antoit, Aithir, Laithluaithi, Sen-chormac, Fedlimid, Angus Buaidnech, Fedlimid Aislingthe, Angus, Eochaid Muin-remor, Erc, Fergus (Mor mac Earca of circa 500 AD).
And Rawlinson’s version is: Áengus Teamrach (81st Monarch), father of Fiachu Fermara, father of Ailill Érann, father of Feradach, father of Forgo, father of Maine Mór, father of Arndail, father of Rothrer, father of Trer, father of Ro-Sin, father of Sin, father of Dedad, father of Iar, father of Ailill Anglonnach, father of Éogan, father of Eterscél (95th Monarch), father of Conaire Mór (97th Monarch), father of Cairpre Finn Mór, father of Dáire Dornmór, father of Cairpre Crommchenn, father of Lugaid Allathach, father of Mogh Lamha, father of Conaire, father of Eochaid (Cairpre Riata), father of Fiachra Cathmáil, father of Eochaid Antóit, father of Achir Cirre, father of Finn Fiacc, father of Cruithluithe, father of Senchormac, father of Fedelmid Ruamnach, father of Áengus Buaidnech, father of Fedlimid Aislingthe, father of Áengus Fert, father of Eochaid Muinremar, father of Erc, father of Fergus Mór mac Earca.
Both sources confirm Hart’s view that Fiachu Fermara ( or Fiach Fearmara) is the ancestor of Fergus Mac Erc and his brother Loarn.
Fergus Mór MacEarca, son of Erc moved the throne of the Dál Riada from Ulster to Dunadd (c500) near where the River Add flows into Loch Crinan in Argyll.
Descendants of Fiacha Araidhe - The Tribe of The Saint
The Eochaidh from whom the Ui Echach Coba claimed descent is reputed to have been a descendant of Fiacha Araide, ancestor of the Dal nAraide .
Eochu Coba (from whom come the Ui Eatach Coba) son of Crond Badruí son of Eochaid son of Lugaid son of. Ros son of Imchaid son of Feidhlimidh son of Cas, son of Fiachu Araide (Dál n-Araidhe). http://www.magoo.com/hugh/ulsterkings.html
According to Carmichael in Lismore in Alba St Moluag's ancestry is given as son of Lucht, son of Finnchadh, son of Fodan, son of Fiacha Araidhe a quo Dalaraidhe. Although the dates would suggest that a few generations have been skipped, it confirms Moncreiffe’s view that Moluag was a Pict of high birth. If one assumes Fodan is the son of Eochaidh rather than Fiacha Araide the dates fit – and it is a plausible confusion as Eochaidh could easily be read as Fiacha Araide.
So Moluag descends from Fiacha Araidhe