I thought what you are showing there are the book lungs - I'm new here and there might be more to your message. I'm here to find out if my B Smithi, named Daisy, if the hooks on her front legs are because she should really be called Danny!
I'm actually trying to show the spermethecae - or lack of one - in between the two upper booklugs along the inside of the epigastric furrow of the exuvium. I think the spider is a male, even though it was sold to me as a female. I see no spermethecae along the fold of the furrow between the upper booklungs. Check the "sexing for dummies" thread stickied on the Tarantula Announcements boards to see what I mean.
I only have had one B Smithi and knew little about spiders, but isn't it widely known that the shop people assure you a young spiderling is the sex you want it to be knowing they might be 50% right!!!
I'm convinced my poor spider has grown up with a personality complex due to me thinking he is a she!