Euphorbia heyneana

Three prostrate species are rather close. I found the following keys in Flora of India:

30 a. Plants prostrate, only branches or tips of branches decumbent; cyathia solitary, paired or 3 together ... 31
b. Plants erect, decumbent or ascending; cyathia more than 3 in glomerules … 33
31 a. Stems and branches pinkish grey; mature capsules remaining within the involucre ... 32. E. thymifolia
b. Stems, branches and leaves green, glaucous-green, purplish green or blackish green; mature capsules protruding out from the involucre 32
32 a. Stems, branches and leaves blackish or purplish green; capsules acutely keeled, with ciliate hairs confined to keels only ... 26. E. prostrata
b. Stems, branches and leaves green to glaucous-green; capsules obtusely keeled, glabrous or sparsely hairy all over the surface ... 13. E. heyneana
33 a. Plants glabrous; leaves linear-lanceolate, 3 - 6 mm wide, glabrous to sparsely pilose ... 17. E. hyssopifolia