This grey-green grass is hairy at the base of the stems (Photo 1). The seeds are layered against one another in the seed head (Photos 2 & 3), and when pulled apart, each seed is the shape of a moderately-broad arrow-head. It seems mostly prolific around human occupied areas so may be an introduced species, or just well transported by human clothing which it readily penetrates and sticks in. There is another grass which occurs in the same area, with a similar, but narrower arrow head seed shape. The seed of that plant is sharp enough to penetrate a dogs skin, and can move subcutaneously through the flesh. That is not true of this plant, although the mechanism of screwing into the soil to germinate is a similar action. This may be the same grass as logged at Sighting 4651439.