Professor Salzberg-
I think I found your fable. It's by Jean de La Fontaine...Hope it's the one you were talking about:

The Oyster and the Litigants--
Two pilgrims on the sand espied
An oyster thrown up by the tide.
In hope, both swallowed ocean's fruit;
But before the fact there came dispute.
While one stooped down to take the prey,
The other pushed him quite away.
Said he, "'Twere rather meet
To settle which shall eat.
Why, he who first the oyster saw
Should be its eater, by the law;
The other should but see him do it."
Replied his mate, "If thus you view it,
Thank God the lucky eye is mine."
"But I have an eye not worse than thine,"
The other cried, "and will be cursed,
If, too, I didn't see it first."
"You saw it, did you? Grant it true,
I saw it then, and felt it too."
Amidst this sweet affair,
Arrived a person very big,
Ycleped Sir Nincom Periwig.[9]
They made him judge,—to set the matter square.
Sir Nincom, with a solemn face,
Took up the oyster and the case:
In opening both, the first he swallowed,
And, in due time, his judgment followed.
"Attend: the court awards you each a shell
Cost free; depart in peace, and use them well."
Foot up the cost of suits at law,
The leavings reckon and awards,
The cash you'll see Sir Nincom draw,
And leave the parties—purse and cards.[10]

[9] Sir Nincom Periwig.—The name in La Fontaine is Perrin Dandin, which is also that of the peasant judge in Rabelais (Book 3, ch. 41), and the judge in Racine's "Plaideurs" (produced in 1668). Moliere's "George Dandin" (produced 1664), may also have helped La Fontaine to the name. The last-mentioned character is a farmer, but, like the others, he is a species of incapable; and the word dandin in the old French dictionaries is given as signifying inaptness or incapacity.
[10] The oyster and lawyer story is also treated in Fable 21, Book 1. (The Hornet and the Bees).

http://oaks.nvg.org/lg2ra11.html