Hello Jann, I think people need more information on this tantalising find - like scale, measurements, texture of surface. Best wishes, Julian

Only other information I have is that it's around dinner plate size. A fisherman suggested a coffin ray. I've attached another pic of it turned over. 

St. Augustine monster comes to mind:

https://en.wikipedia.org/wiki/St._Augustine_Monster

Jann, a ray certainly came to mind when I saw the creature's 'mouth', and a coffin ry would work for Australia. But I'm not an expert, and there are many other types of ray, some of which might fit better. 

Thanks Julian.

I also agree with a coffin ray.

See : http://australianmuseum.net.au/image/numbfish-on-the-beach

Fred

I also agree with a coffin ray, in the second picture the teeth are clearly visible. With the teeth and the picture you may probably get it identified to the genus level. 

Consider contacting NSW Fisheries (http://www.dpi.nsw.gov.au/fisheries) - they can likely tell you what ray or skate species this is.  Foetus (fetus) is usually reserved for mammalian species - which this is not.

Thanks Douglas, I wasn't aware that foetus was reserved for mammals. I'll send the pic to fisheries.  

A dorsal photo would have been more helpful but this little guy is an electric ray most likely Hypnos monopterygius which is common in NSW. I think that's what Australians refer to as the 'coffin ray'

The fish of photography presents a ventral view, and Maybe is a blobfish that was named the World's Ugliest Animal, here another picture

It appears to be a torpedo ray (elasmobranchii: Batoidea,Torpediniformes).  It may well be a coffin ray (Hypnidae: Hypnos monopterygius) as others have already suggested, but I am unfamiliar with that particular family of torpedo ray. 

Douglas is correct in that the term fetus (foetus) is reserved for use in mammal biology, especially in reference to humans.  This ray may have been a full term embryo, or a neonate.  

Thanks Jason and Douglas. My background is originally in writing/editing and the word fetus  (apparently foetus is a learned Latinism!) in Latin means the 'young while in the womb or egg … the bearing or hatching of young ... a bringing forth', which doesn't tend to suggest that the original Latin word denoted only human or mammalian offspring. I understand, however, that it is now used generally in mammalian (particularly human) biology.