They replace injured spinner Rangana Herath and pacer Nuwan Pradeep, while batsman Danushka Gunathilaka has been dropped.
Chameera had been troubled by injuries off late and last played Test cricket against New Zealand in 2016. Gamage featured in the two-day practice game against India in Colombo before the start of this three Test series.
With their addition, interestingly Lanka now have four quick bowlers in their squad for the Pallekele Test, including Lahiru Kumara and Vishwa Fernando.
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