A 38-year-old female has come to infeility clinic. She complains of inability to conceive. Sperm analysis of the paner is given below. Semen volume 2 cc Sperm density 20 x 10 6/cc Sperm motility 50% Sperm morphology (strict criteria) 14% Sperm bility 40% White blood cells - Hysterosalpingography was done in the patient with recurrent aboions which gave the following finding The condition marked by black arrow is due to mal-development of which structure?