Crassula muscosa is better known as Crassula lycopodioides, and now placed in synonymy. It is a dense scrambling bushy perennial succulent 100-400 mm tall; the slender branching stems are slightly woody, densely covered by small, scale-like, neatly overlapping, leaves arranged in 4 rows. In spring, produces tiny, 5-petalled, greenish-yellow flowers. C. lycopodioides is probably the commonest species of all, and comes in various leaf sizes and colours; slenderness and robustness is equally extremely variable.
Source: The Encyclopedia of Succulents