Some mob heads are broken/missing

When I use the give command to obtain custom skulls, sometimes it doesn't work. The broken one is the biggest concern, the missing ones aren't as important.

Broken:
MHF_Blaze

Missing:
MHF_Bat
MHF_EntityHorse
MHF_Wolf
MHF_Silverfish
MHF_Witch
MHF_SnowMan
MHF_EnderDragon
MHF_Endermite
MHF_WitherBoss
MHF_Guardian
MHF_Rabbit