Bennett Fracture - “oblique intraarticular metacarpal frx (known as the palmar beak fragment) which remains attached to the palmar beak ligament”

from: http://www.wheelessonline.com/ortho/bennetts_fracture_dislocation

compared to the comminuted version : Rolando fracture http://www.learningradiology.com/notes/bonenotes/wristfxs.htm