Can Engulfed creatures be targeted with non-area spells without hitting the transparent or translucent Engulfing creature?

Oozes like gelatinous cubes can use the Engulf ability. If a caster can see an Engulfed creature since the ooze is transparent or translucent, can the caster target the Engulfed creature with a non-area spell without hitting the ooze?

My inclination would be that any area-based spells such as those with bursts or lines would hit the Engulfing creature (and possibly the Engulfed creature, as well). But spells like Heal simply allow the caster to select a target.

So could a caster target an Engulfed ally with a Heal spell without healing the Engulfing creature, assuming the caster could see (or otherwise perfectly sense) the target?