Galium normanii. The slender bedstraw is quite common all over Iceland. It grows on drier soils like gravel plains, hill sides etc. The plant trails over the ground. Characteristic too are the whorles of many leaves (at least 6, more often at least 8 leaves in a whorl).
It is a member of the Madder family (Rubiaceae). The Icelandic name of this species is Hvítmaðra.