The species Carl compares to the alien lower half of Eileithyia's true face.
When Eileithyia appeared in her true form for the first time, her olive skin, dark eyes and dark curly hair were all human — but her lower face was not, which surprised Carl given the Greek nature of her name.
He described the alien half of her face as almost nullian-like: kind in expression, yet distinctly not human.
The reference point for the alien half of a goddess's face.