Ostracodes ( http://en.wikipedia.org/wiki/Ostracod) are a class of the Crustacea and very difficult to photograph, because their body has two valves, which are not very transparent. "My" Ostracode was 1250 µm long. The eye is in the middle of the body.
The species could be a Cypridina (mediterranea?), but I am not at all sure about it.
First picture: Obj. 4x, achromatic, brightfield
Second picture: Obj. 10x, DIC
third picture: Obj. 4x, achromatic, brightfield.
Images made through a microscope. All subject types.