I'm just knowledgeable enough to know that these are not standard bombs under the wing of a VA-63 FJ-4B:
Emil Buehler Library, National Museum of Naval Aviation
And there is a second picture of one being jettisoned from a different VA-63 FJ-4B:
Emil Buehler Library, National Museum of Naval Aviation
But wait, there's more: the photo caption for the first picture indicates that it was taken on 9 September 1958, shortly after the squadron had begun a deployment aboard Midway (CVA-41). A stores-carry and jettison evaluation by a squadron at sea? That seems unusual even though those were somewhat more permissive times in Naval Aviation.
Close examination of the store suggested that it might be an AJ Savage tip tank with the addition of a tail fin kludge (for one thing, the fins are externally braced).
Note the clear nose and that they might be painted sea blue. The FJ-4B store seemed a bit longer than the AJ tank but that could have been a modification, like the addition of the shackles and fins. (The FJ-1 Fury carried a similar tip tank and an longer version was used to provide the range, just barely, for the Bendix Trophy "Race" in 1948.)
As a result, I had thought that it might have been a kludge to provide a source of external fuel tanks because not enough of the unique FJ-4 drop tanks were available for this deployment, one of the first for the FJ-4B.
Another guess was that it was a revisit to a home-grown napalm bomb concept to have on hand for crowd control if necessary. That turned out to be close. As Gerry pointed out in his comment below, it is actually a standard 750-lb Mk 77 fire bomb with the Mk 19 bomb conversion kit. It does in fact have a clear nose cone over the igniter. The addition of tail fins in the bomb kit allowed it to be dropped from a dive as opposed to a low-level pass.