Distribution of GCs in energy-action space or (J_ϕ, E), (J_R, E), and (J_z, E) space. The grayscale background shows the halo MSTO stars from Myeong et al. (2018a) as a comparison. There are 75 GCs with Gaia DR2 proper motions and a further 16 with Hubble Space Telescope (HST) proper motions; 53 OHs (red circles), 17 YHs (blue triangles), 16 BDs (yellow triangles), and 4 Sgr GCs (SG; green diamonds) together with one of unknown classification (gray cross). Sgr is also marked as a black filled square. The vertical dashed line marks the division between prograde (J_ϕ > 0) and retrograde (J_ϕ < 0). The horizontal dashed line signifies the characteristic energy above which all of the YHs lie, and below which all of the BDs lie. The eight OH globular clusters, with symbols that are enclosed by black open circles, are grouped together in (J_ϕ, E) and (J_z, E), while in (J_R, E) they are stretched out close to the boundary of J_R at corresponding energy (as judged from the MSTOs). They are the Sausage GCs. The two YHs enclosed with black open squares form an extended selection that may also be related. They have horizontal branch morphology similar to OHs, and have similar actions.