[CONNECT MicroStationAPI] Where is the element type enum?

I can see where element types are used in DgnElements.h.  For example...

#define TMSK0_CELL_LIB          ELMBITMSK (CELL_LIB_ELM)
etc.

However, I can't see where those values are defined.  Is there an enum { CELL_LIB_ELM, .... } that hasn't been published?