Great song - very difficult to find. This is direct from one of Don's songbooks - I worked it up a while ago. Note that the [Em7] is played on a short pause between words.

On The Amazon
Sung by Don McLean
Words by Clifford Grey and Greatrex Newman, music by Vivian Ellis
From 1927 British musical, "Mr. Cinders"

[Gm]There's a danger [D7]zone, [Gm]not a stranger [D7sus4]zone [D+] [D]
[Gm]Than [Gm7]the little [Cm7]plot I walk [Cm6] on [A7-9]that I [A7-5]call [A7]my [D7]home.
[Gm]Full of eerie [D7]sights, [Gm]weird and skeerie [D7sus4]sights [D+] [D]
[Gm]Ev'ry vicious [Cm7]animal [Cm6] that [A7-9]]creeps and [D7]crawls and [Gm7]bites.

[D7]On the [G]Amazon [Em7] the prophy-[Am7]lactics [D7]prowl,
On the [G]Amazon [Em7] the hypo-[Am7]dermics [D7]howl,
On the [G]Amazon [Em7] you'll hear a [Am6]scarab [D7]scowl
And [G]sting, [E7] [Am7]zodiacs [A7-5]on the [D7]wing.
All the [G]stalactites [Em7] and vicious [Am7]verte-[D7]brae
Hunt the [G]stalagmites [Em7] while laryn-[Am7]gitis [D7]slay
All the [G]parasites [Em7] that come from [Am6]Paraguay in [Am7]Spring...[D7]mmmmmm
[Dm7-Gbass]Snarling [C]equinox a-[Cm]mong the rocks will [G]seize [F#] [F] [E]you,
[E7]And the [A7]Fahrenheit comes [Am]out at night to [D9]freeze you.
[D7]Wild du-[G]odenum [Em7] are lurking [Am7]in the [D7]trees
And the [G]jungle swarms [Em7] with green a-[Am6]postro-[D7]phes.
Oh, the [G]Amazon [Em] is [Am7]call-[D7]ing [G]me. [C#dim] [Am7]

On the Amazon the pax vobiscum bite,
On the Amazon the epiglottis fight,
On the Amazon the hemispheres at night all slink,
Where the agnostics drink.
All the hippodromes that lie concealed in mud
Join the metronomes that live in swamp and flood;
Then the kodachromes come out and drink their blood,
Poor ginks.
While velocipedes among the weeds will scare you,
And the menopause with hungry jaws ensnares you.
Frenzied adenoids infest the hills and slopes,
Ev'ry one avoids the deadly stethoscopes.
Oh, the [G]Amazon [Em] is [Am7]call-[D7]ing,
Yes, the [G]Amazon [Em]is [Am7call-[D7]ing,
Oh, the [G]Amazon [Em] is [Am7]call-[D7]ing [G]me.