Drawing latitude and longitude lines in matlab using Geoshow

I'm trying to divide up a map by drawing lines at latitudes and longitudes. I bring in the map using

geoshow('landareas.shp', 'FaceColor', [0.5 1.0 0.5]);

Then

geoshow([-150 90],[-150, -90])

But I need the line to follow the latitude or longitude line. For example, I need a line to divide up the world at longitude -150, -30 and 90

Can anyone give me a tip on how to easily accomplish this?

Thanks

-Kallie

[Kelly Kearney]

Are you using a map axis, or just plotting to a regular axis?