The pelvic Cavity.

http://en.wikipedia.org/wiki/Pelvis

• the pelvic cavity, typically defined as a small part of the space enclosed by the bony pelvis, delimited by the pelvic brim above and the pelvic floor below; alternatively, the pelvic cavity is sometimes also defined as the whole space enclosed by the pelvic skeleton, subdivided into:
  • the greater (or false) pelvis, above the pelvic brim
  • the lesser (or true) pelvis, below the pelvic brim
• the pelvic floor (or pelvic diaphragm), below the pelvic cavity
• the perineum, below the pelvic floor