Cerastium nigrescens; the Arctic Mouse-ear is a mouse-ear species that is more restricted to the higher altitudes and interior of Iceland than other mouse-ears. The most striking feature of this plant is its shiny green colour - compared to other Cerastium's. I personally find it difficult to distinguish it from the very common Alpine Mouse-ear, but the combination of greener (more shiny) leaves and the lesser tomentose hairyness feature are typical characteristics (note: the arctic mouse-ear also has hairs on the stems and leaves - they are less dense though, and especially on the leaves only on the margins). Furthermore the petals of the Arctic Mouse-ear are less incised in the middle than the ALpine Mouse-ear. Another differentiating characteristic are the broader (somewhat boat-shaped) calyx leaves. For other differentiating characteristics of other Icelandic mouse-ears see the page on the alpine mouse-ear. The Latin name of this species has been Cerastium arcticum but the concensus among specialists is now that the name is Cerastium nigrescens. Having said this though, there is no concensus about sub-species level. Some consider the species growing in northern Europe (and Iceland) to be the sub-species "arcticum" where others consider the Icelandic species to be the variety "laxum".
It is a member of the Pink family (Caryophyllaceae). The Icelandic name of this species is Fjallafræhyma.