The specific name, knoxii, is in honor of Scottish anatomist Robert Knox.

[3] Adults of M. knoxii usually have a snout-to-vent length (SVL) of 5.5–6.5 cm (2.2–2.6 in).

Dorsally, the body is brownish, with a striped and spotted pattern.

Ventrally, it is bluish gray to cream-colored, except during breeding season when males have a bright yellow chin, throat, and anal region.

[4] M. knoxii occurs in Namibia and South Africa.