Armen Martirosian mentioned the 13th satrapy. I want to add few notes in this subject.
The Greek sources about Armenia should be examined with great cautious. They are different from cuneiform writings which are left by state just at the moment of the event.
Here I attach a map of Achemenid satrapies which is based mostly on Persian sources. Greek sources that contradict to Persian one are ignored. As one can see there are no such things like 13th or 18th satrapies. There is a large Armenia divided in three regions one of which is the Colchis. Eastern border of Armenia satrapy reminds us the borders of Urartu which didn't controlled fully the Urtekhi (Artsakh) while the Etiu is fully in Armenia. So where are those Alaroid, Saspires and Matienes? Well the only source about this tribes and their mysterious 18th satrapy is the Herodotus . You can see the list of sources here.
There is no other source about 18th satrapy other than Herodotus. Even more non of this tribes can be securely linked to preceding cuneiform texts. Just to understand how reliable they are let's remember the so called Paktika mentioned as part of 13th satrapy with Armenia. I couldn't find a toponym that one can link with this term. Well Paktika do exist but it is in Afghanistan.
So if we find such a confusion then we can expect confusions elsewhere also.
Saspir - No mention in Urartu. It is probably related to Sper with extra Kartvelian Sa prefix. Then this tribe was living in more Western region north of Erzrum Alternatively Saspir was a Scythian tribe from which Sper ( modern Ispir) derives. If they were Scythians so they would barely had an impact on locales.
Alaroid - Even more puzzling because it supposedly appeared in the place of Etiu. Some linked it to Urartu. The theory was that Urartians have found refugium in modern Armenia. But that is quite dubious if we take into account the archaeology. One possibility is that this name is a distorted version of Haldiuri mentioned in cuneiform in more Western regions. The other possibility is that it represent Udur-Etiu. With d->r transition becoming Ururetiu. And finally it is the oldest mention of Ayrarat province. Anyway it is quite doubtfull that it was a new tribe unrelated to preceding tribes.
Matieni - was living in the place of Mannai. Once more the link with Mitanni attested at LBA is very dubious. No mention of Mitanni exist at Iron Age. Quite possible it was an offshoot of Medes Iranian tribes. But there is another solution. It is yet another distortion, from Mannai. Other historians mention them as Mantieni or even Martuni.