#2 is a batfish (Ogcocephalidae)

# 3 is a hammerhead (genus Sphyrna), though there are several species it could be.  My guess without better photos or my book in front of me is that it's likely a smooth hammerhead (Sphyrna zygaena) or a scalloped hammerhead (Sphyrna lewini).  Photos of the head from the top can be a good diagnostic feature for hammerheads. 

Information about where the fish were caught can help narrow down your search, as would photos from additional angles.  

Hope this helps.

1) Acipenser sp.

2) Ogcocephalidae as said Godfried Van Moorsel 

3) Sphyrna sp. as said Rob Nowicki 

4)  Squatina squatina (Angel shark).

Best regards

Hi dear Manon

The first pic is related to a Sturgeon and likely Acipenser nudiventris.

Alfonso has it right, it is a Squatina.

And about the Hammerhead, I think it is Sphyrna zygaena. Good luck

The first picture is obviously a sturgeon, though I am not sure that it is  Acipenser nudiventris as Milad Khosravi suggested. There are over two dozen sturgeon species, of which most are in the genus Acipenser.  Given that the City of Toulouse bisects the River Garonne, I wonder if the specimen is  the native species Acipenser sturio.  To properly identify the species, having the location of where the specimen was collected is important. It is very hard to identify a sturgeon based on pictures taken from the side or from above.  Many of the characteristics that distinguish sturgeon species are ventral (barbel counts or shapes, mouth shapes, vent position relative to anal fin, scute patterns posterior to the vent, coloration and patterns, etc.).  Might I suggest you check out the World Sturgeon Conservation Society website (http://www.wscs.info) Not only will you find a webpage on the various species, but also if you look at the About webpage, and select Contacts, you will see information for Patrick Williot, the WSCS France and Belgium contact person.

I believe Sturgeon is Acipenser Oxyrinchus but I'm not sure if it's 

Oxyrinchus Oxyrinchus or Oxyrinchus Desotoi

Hi everyone  ! 

I think indeed that Acipenser nudiventris as a nose smaller than my sturgeon. Unfortunately the problem with all my specimens is that I have no idea of the place they were collected, some of them are even from the XIXth century, so nobody can tell me where is it from ! 

Thanks a lot for all your help, 

here's a picture of the ventral face of the sturgeon, they are not very good I'm sorry !

For the sturgeon, please consider Adriatic sturgeon (Acipenser naccarii)

The third fish from the top could be a toad fish (Batrachoididae)

I think Godfried Van Moorsel  is right

#2 is a batfish (Ogcocephalidae), perhaps Malthopsis jordani?

Thanks a lot, the website is very helpfull ! I will have to check with specialists indeed, I hope I'll find some at my museum !