That "pillbug" was a 7-passenger car with a single driver's seat in front between the front wheel wells followed by 2 rows of 3-abreast seating with an air-cooled in-line 4 engine in the back. It was a research vehicle built on the frame of a Mercedes-Benz 170H W28 by Professor Schlör at the Technical university of Gottingen in 1937 and was lost during WWII. But it looks like the guys at that website are working on building a reproduction of it on a MB 170 frame that they have.
Another website with pics of German streamlined cars:
On those sites they mentioned the book: Stromlinienautos in Deutschland by Ralf J.F.Kieselbach. Sounds like an interesting read.