why does the daylight Moon appear to have a 'horizonal' shadow?

[balladofserenity]

why does the daylight Moon appear to have a 'horizonal' shadow? I know it's know exactly horizonal but certainly it isn't vertical. It does not appear to have phases such as new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter or waning crescent. But it does appear that the daylight moon's lower quarter or lower third is shadowed by the Earth. What is the spatial orientation of the Earth, Moon and Sun to create this effect?

[swansont]

If we are viewing the moon from the side as it faces the sun, the demarcation of light/dark will be a line.

[Delta1212]

Was the Sun above it in the sky? I would think the bright part of the moon should be oritented towards the sun and the shadow should be opposite the direction of the sun, since the sun is the light source that is illuminating it.