Lipina grouped these specimens, that show sheets of cells, together with others that are clearly tubiform, but we do not see convincing evidence that these specimens are taxonomically related.
Halysis is distinguished from the Microproblematicum Flabellia by not being tubiform.
Processes generally hollow, tubiform to tapering, sometimes with striae and annular thickenings along their length; they are distally open or closed and furcated.
It has subsequently been interpreted as a tubiform green alga and as a cyanobacterium, and Ordovician specimens that are evidently Halysis have been referred to the filamentous green alga Oedogonium Link, 1820.