Monster missing from list

Helmed Horror

Filters for "Legendary" & "Lair" seem to produce no results...

.

What determines if it SRD or not.. Like I don't see beholder. Is it a mistake or it does not appear in SRD.

Thanks

Ok I think I found it... 

I saw that as well.  Looking further through this thread it states they're using the SRD.

A quick search through the SRD shows that it talks about lair actions, and some stats even refer to them as well.

However, none of the Monster Stat Block actually list their Lairs and corresponding Actions.  So at this point, they're fine.

Side note, the L in the Black Hex next to a Monsters name, indicates that they have Legendary Actions.