Indra and Vasi.s.tha

[N. Iyanaga]

I have a question.  I find in a collection of Jaataka (Taisho 153, 
translated in Chinese by Zheqian, in 3rd century) a version of the 
Jaataka of the king Candraprabha.  The story is:
The King Candraprabha decides to give all his possessions to his 
people.  A wicked brahman who practices in the Himaalaya, comes and 
insists on the head of the King; he says "If the King is decided to 
give all, he should give me his head", etc.  The ministers are 
outraged and protest, but the King offers his head...
In this story, there is a passage in which the brahman makes a parade 
of the power of the brahmans, and there, he enumerates some of the 
famous exploits of the .r.sis (or ascetics?):
"...Thus the .r.si Jahnu took down the water of the river Gangaa, and 
its flow stopped during 12 years; thus the god Ii'svara has 3 eyes; 
thus the .r.si Gautama marked Indra with a thousand yoni on his body; 
thus the .r.si Vasi.s.tha changed Indra in a goat (or ram??)...", etc.

I could find some references on the first 3 "exploits", but I could 
not find any about the last one ("Vasi.s.tha changed Indra in a 
goat").  Is this an element in the classical mythology?  Would someone
 give me some references on this story?

In connection with this, I found in _Epic Mythology_ of E. W. Hopkins 
(p. 135) a passage which recalls very closely this enumeration:
"...In 13, 34, 27, this [i.e. the fact that Indra has been cursed by 
Gautama with a thousand sex-marks which became eyes] is cited as proof
 of priestly power, since Kau'sika Gautama was a priest; priests also 
cured Indra: "Behold, a mark was made on the moon (by a priest); the 
sea was made salt (by a priest); and great Indra was marked by a 
thousand sex-signs, who yet by the might of Bhraahma.nas became 
thousand-eyed..."
Is this a kind of cliche in the mythology?

I would appreciate any reference, suggestion and idea.  Thank you very
 much in advance!
Best wishes.
Nobumi Iyanaga
Tokyo,
Japan