As the caption 'The Shapes Familiar to the Spirits of Saturn' suggests, I believe the forms — certain animals, plants, leather jackets and other carriers of aesthetics, behaviour and physical bodies — communicate forth ideas, functions and geometric shapes that in the holistic human interface can be seen as part of some whole (a spirit). Saturn is a great example for isn't it the spirit which gives material existence to all the ideas? As it works as part of the whole (from one aspect all the others can be found) in giving the physical form, through it comes all the other angles to the physical plane. If we are to think of spirits as certain geometrical angles or a group of angles, I interpret from the quote Saturn to have quite a narrow angle as its familiar shapes are tall, lean and slender bodies. Meanwhile Saturn in its duty of making the material aspect of the universe also puts forth the wider angles of other spirits on that plane. In this way I see depictions of spirits and gods almost geometrically definite.
Yet the exact angle(s) or spectrum remains indeterminate, atleast in these examples, and thus it is symbolic in the same lively manner the world goes and morphs by without stopping on a definition. By the holistic human interface, I referred to, we make interpretations and are more or less able to see the unifying core of a spirit in it's seemingly reduced layers of existence – the forms, ideas, functions etc. Seeing a spirit behind these poetic presentations is seeing the manifested world as an image of god, and in this the definite and symbolic blurs in to one, after which question of factuality seems almost ridiculous. (It is easy to say these interpretations are just subjective fantasies, but to me it usually seems like giving up before seeing all the evidence or metaphysics behind the thought.)
Sometimes it is obvious the symbols of the natural world does not meet, for example, the actual animals nature. There the writer might have had some striking intuition from a miniscule detail or the painter might have build on a tradition that has become a bit "rigid", or more positively expressed stone-like in its symbolism. The question of validity of symbolism beautiful but distanced from the depicted imagery has been bugging my left hand a bit. But there's also some strange beauty in these, for example, the pelican feeding its progeny with its own blood – a depiction uniting Christian symbolism and (I would assume) European folk lore. The basic sacrificial idea comes across including many subtle meanings of cultural exchange etc. that might be interpreted to also be in the area of Christ/Mercury, the latter which is the god of commerce and communication. There's so many layers the manifested material world has to give it's face to, that it is no wonder it often might seem so chaotic.