An Allusion to Keats?

Another of Mifflin's classically-themed sonnets is called 'An Elegy'. I was reminded of Keats due to the following bolded rhyme.

Immortal laurel of no growth terrene,
Gather, ye Muses, in Olympian air;
'T is for a shepherd, loved of Pan, to wear;
Behold him lying on the headland green
That juts above the sea in this demesne,
As still as sculptured marble, and as fair.
Ye will not wake him if ye crown him there;
Wreathe him the while he seems to sleep serene.
The syrinx now lies useless by his head...
Was that a sigh within the cypress near?
Oh, soft, ye Muses!--softly round him tread,
Bring all your late reluctant garlands here;
Relax your haughty mien; ye need not fear
To crown this Dorian now--for he is dead!

The rhyme of 'demesne' and 'serene' occurs here in lines 5 and 8. Keats' poem 'On First Looking into Chapman's Homer' is also in sonnet form. In addition, the rhyme-scheme is the same in the two poems except for the last two lines (Mifflin: abbaabbacdcddc; Keats: abbaabbacdcdcd). But Mifflin's 'a' line-ending ('-ene') is Keats' 'b' line-ending. Thus, though the 'demesne-serene' rhyme occurs in the same four-line segment of Keats' poem, it is in lines 6 and 7 instead of 5 and 8.

Much have I travell'd in the realms of gold,
And many goodly states and kingdoms seen;
Round many western islands have I been
Which bards in fealty to Apollo hold.
Oft of one wide expanse had I been told
That deep-brow'd Homer ruled as his demesne;
Yet did I never breathe its pure serene
Till I heard Chapman speak out loud and bold:
Then felt I like some watcher of the skies
When a new planet swims into his ken;
Or like stout Cortez when with eagle eyes
He star'd at the Pacific--and all his men
Look'd at each other with a wild surmise--
Silent, upon a peak in Darien.

(Text here.)

It seems probable to me that this particular rhyme (especially with the rather uncommon 'demesne') was borrowed from Keats, but of course I may well be wrong about that. Has anyone come across it elsewhere before?