[Inkscape-user] Getting basic fonts to show up correctly

A newbie here trying to understand fonts in Inkscape on Mac OS X (10.4.6):

Basic fonts like Arial, Georgia, and Verdana are not showing up with their entire families in the Text and Font box.

Arial, for example, doesn't show up, but 'Arial Black', 'Arial Hebrew', 'Arial Narrow', and 'Arial Rounded MT Bold' does.

In another example, Georgia does show up, but its other family members, such as italic, bold, and bold italic, are not present.

Anyone have tips on solving this issue?

Thanks.