Many people refer to those as "proportional" bikes. They were popularized by Terry. The smaller 24" front wheel is usually found only in the smaller sizes. Similar bicycles were made by Bianchi and some others. The idea was to build the bike with a smaller front wheel to get the frame size small enough (usually down to 41cm) without the problem of "toe overlap" . More info on smaller women specific bikes can be found here.
http://www.terrybicycles.com/

Zagnut