Some other avatAras of viShNu are described in this chapter of harivamsa:
bhUyo bhUta-Atmano viShNoH prAdurbhAvo mahAtmanaH |
dattAtreya iti khyAtaH kShamayA parayA yutaH ||1-41-104 tena naShTeShu vedeShu prakriyAsu makheShu cha | chAtur-varNye tu saMkIrNe
dharme shithilatAM gate ||1-41-105 abhivardhati cha a-dharme satye
naShTe a-nR^ite sthite | prajAsu shIryamANAsu dharme cha a-kulatAM
gate ||1-41-106 saha-yaj~na-kriyA vedAH prati-AnItA hi tena vai |
chAtur-varnyam a-saMkIrNaM kR^itaM tena mahAtmanA ||1-41-107
At another time, viShNu, the soul of all, incarnated himself as the highly forgiving datta-Atreya. When the veda-s disappeared,
religious works and Vedic rituals slackened, four-caste system became
hotchpotch, when dharma is collapsing and a-dharma is on the rise,
when truth is lost and untruth flourished, when all people are about
to face a cultural perish, when dharma is floundering in the morass of
a-dharma, lord dattAtreya re-established the four Vedas with their
rituals, and re-categorised the four caste system, as well...
navame dvApare viShNuH aShTAviMshe purA abhavat |
vedavyAsaH tathA jaj~ne jAtUkarNya puraHsaraH ||1-41-161 eko vedaH chaturdhA tu kR^itaH tena mahAtmanA | janito bhArato vaMshaH
satyavatyAH sutena cha ||1-41-162
After the ninth incarnation of viShNu, the lord having sent beforehand sage jAtUkarna to study veda-s and purANA-s, took his birth
as sage veda-vyAsa in the twenty-eighth dvApara era, to segregate
one veda in four sections, and even to categorise purANA-s, for easy
comprehensibility... This sage veda-vyAsa, engendered by lady
satyavati, is the originator for the dynasty of bhAratA-s...
This chapter of harivamsa describes avatAra kapila:
AseduH te tataH tatra khanyamAne mahArNave || 1-14-23 tam Adi-puruShaM devaM hariM kR^iShNaM prajApatim |
viShNuM kapila rUpeNa svapantaM puruShottamam || 1-14-24
Then those princes unremittingly dug the place to oceanic depths until they reached shrI-hari reposing there in the getup of sage
hayagriva avatAra of viShNu described in this chapter
"Thus did the blessed Hari assume in days of old that grand form having the equine head. This, of all his forms, endued with
puissance, is celebrated as the most ancient. That person who
frequently listens or mentally recites this history of the assumption
by Narayana of the form equipt with the equine head, will never forget
his Vedic or other lore.....
Quadruple form - Nara, Narayana, Hari, Krishna described in this chapter
O monarch, during the epoch of the Self-born Manu, the eternal Narayana, the Soul of the universe, took birth as the son of Dharma in
a quadruple form, viz., as Nara, Narayana, Hari, and the Self-create
vatapatrashayi avatAra in this chapter
O king, wandering without cessation, through that flood, I become fatigued, but I obtain no resting place! And some time after I behold
in that expanse of accumulated waters a vast and wide-extending
banyan tree, O lord of earth! And I then behold, O Bharata, seated on a conch, O king, overlaid with a celestial bed and attached to a
far-extended bough of that banyan, a boy, O great king, of face fair
as the lotus or the moon, and of eyes, O ruler of men, large as petals
of a full blown lotus! And at this sight, O lord of earth, wonder
filled my heart...
mohiNI avatAra in this chapter:
Thereupon Narayana called his bewitching Maya (illusive power) to his aid, and assuming the form of an enticing female, coquetted with
the Danavas. The Danavas and the Daityas charmed with her exquisite
beauty and grace lost their reason and unanimously placed the Amrita
in the hands of that fair damsel.'"
Prithu avatar in this chapter of Drona Parva and this chapter of Santi Parva too.
This high declaration of the Srutis is current among men that Prithu is the eighth from Vishnu.
vyuha avatAras i.e. Caturvyuhas are mentioned in this chapter:
The person who realises that inconceivable Purusha and comprehends his subtile existence in the quadruple form of Aniruddha, Pradyumna, Sankarshana, and Vasudeva and who, in consequence of such comprehension, attains to perfect tranquillity of heart, succeeds in entering into and identifying himself with that one auspicious Purusha.
Vishnu's submarine fire form- Samvartaka in this chapter of Harivamsha:
yaH purA hi analo bhUtvA aurvaH saMvartako vibhuH | pAtAlastho arNava gataM papau toya-mayaM haviH || 1-40-19
How, in the days of yore, did he sip the subterranean lava-like oceanic oblation assuming the form of a submarine-fire, called samvartaka agni...
Lord Vishnu already assumed in the form of Vishvarupa, before Sri Krishna shows this form to Arjuna. It is mentioned in the same chapter of Harivamsha:
sarva devamayaM kR^itvA sarva Ayudha dharaM vapuH || 1-40-22
garudaH tena cha utsiktaH kAlanemir nipAtitaH |nirjitaH cha mayo daityaH tArakaH cha mahAsuraH || 1-40-23
Who is he assuming the consistorial form of all gods, wielding every weapon with every limb, while his eagle-vehicle garuDa proudly airlifted him, slew the demons called kAla-nemi... besides, who is said to have vanquished demons like maya and tAraka...
Sanatkumara is indirectly mentioned as Vishnu's avatAra in this chapter:
He that takes his rise, from that Sankarshana, by his own acts, Sanatkumara, and in whom all creatures merge when the universal dissolution comes, is the Mind of all creatures and is called by the name of Pradyumna
This chapter describes Prishnigarbha Avatar and Lord Vishnu's 7 avatars as Aditi's son:
You have, as said in the Puranas, taken thy birth seven times in the womb of Aditi. It was thou that tookest birth in the womb of Prishni.
The above text says Vishnu incarnates seven times as Aditi's son, according to the Puranas. Maybe, See the Puranas to any reference for it.
Lord Vishnu's bull form described in his chapter:
Then Narayana, issuing out of the point of that shaft, assumed the form of a bull and raised that large car.
Vishnu's elephant form in this chapter of Harivamsha:
sarvakAmaphalairvR^ikShairvR^itaM ramyairmanoramaiH | chakAra ku~njaraM chaiva ku~njarapratimAkR^itim ||3-35-19 The mountains, covered by beautiful trees, pleasing the mind, fulfilled all desires of the mind. Then the Lord created the mountain ku~njara as well in the form of an elephant.
Harihara (Sankaranarayana) form in this chapter of Anushasana Parva and this chapter of Harivamsha.