Gerald, I have the system you're talking about in my workshop and grain system. Here, they refer to it as a 4-wire delta system. Two of the phases to ground is 120V and the third one is 208V -- poorly regulated. Electricians hereabouts refer to that wire as the 'high leg'.

Two wire 3-phase, or commonly referred to as either vee-phase or open delta is used some around here. The phases that are directly fed from a single transformer output are just called regular legs. The third phase that is obtained by connecting to the open ends of the two transformers is commonly referred to as the 'wild leg'.

Convention according to code; on 4-wire delta is to have the high leg in the middle lug in premises wiring and marked with yellow tape. Outside on the meter pole and inside the main disconnect, the high leg is on the furthest right lug and will be marked with blue tape. Installations with higher loads of either single phase 230V & 3-phase 230V, and moderate 120V loads are a good match for the 4-wire delta setup. Not a real ideal setup for places that have a relatively high demand for 120V circuits.