There are two different types of pentatonic scale, the major pentatonic and the minor pentatonic which is shown below. As well as the flattened 7th degree, the minor pentatonic also contains a flattened 3rd degree. The scale degrees of the minor pentatonic scale are 1, b3, 4, 5 and b7.
Because of the way the harmonica is tuned, it is only possible to play the cross harp minor pentatonic scale on the low end of the harmonica. The scale is shown in the following example starting on hole 2 and finishing on hole 6, along with part of the scale on the very low notes down as far as the 4th degree (C).
Here is a riff you learnt in lesson 11 which is derived from the minor pentatonic scale. As you can hear, this scale is great for creating Blues sounds. It is also the most common scale used in Rock.
Here is another lick which is derived from the minor pentatonic scale. Try making up some of your own licks from this scale.