The Birth of Venus

Aka Nascita Venere, aka Simonetta Vespucci.

I like digital jigsaws, it saves loosing pieces under the table but this one has been exceptionally difficult considering:- 

I own a female body
I have studied Human Biology
I have done a bit of marine Biology
I have studied Art

So why is it I can't tell the difference between a woman's body and a scallop shell.