May be you'll find what you are searching  in Horn & Kahle, 1937. " Über entomologische Sammlungen, Entomologen und Entomo-Museologie". The book is near a complete collection of biographies, collections, pictures of labels etc., in Entomology

P. Fischer is mentioned as collector in "Die Forschungsreise "S.M.S. Gazelle" in den Jahren 1874 bis 1876. 3. Teil Zoologie und Geologie.

See:

https://books.google.at/books?id=ECcJx-TbbOIC&pg=PA19&lpg=PA19&dq=%22P.+Fischer%22+collect&source=bl&ots=iG-Mz2MQpP&sig=Kzcy2li99nADhDxz2ckc-rWWZQY&hl=de&sa=X&ved=0ahUKEwiojp2SjuvKAhVEqHIKHQYnDqwQ6AEIQjAG#v=onepage&q=%22P.%20Fischer%22%20collect&f=false

Kind regards Gerhard

Thanks a lot for these interesting ideas!!

Dear Olivier,

I think that Paul Henri Fischer is meant. You'll find more information on him e.g. in Journal de Conchyologie, 42, 1894, 5–12 or Bulletin de Société Geologique de France, 23, 1895, 203–224

He also worked at least on fossils from Syria.

Regards, Klaus

Thanks a lot Klaus!

Or it can be his relative Dr. Paul Fischer, 1898-2003. See Molluscan Research 24(2):131-133

Thanks Stephane!

This mystery is near solved.