The gills of eurypterids were situated in covered pre-abdominal chambers.  They were specialized vascular tracts of the ventral body wall and are known as kiemenplatten.  They have patterns of small spines covered in hexagonal rosette projections.  They may have trapped water and allowed the primarily water dwelling eurypterida to make occasional excursions on to land by acting as terrestrial lungs.

Eurypterids also have 'book lungs' contained within the branchial chambers.  These are similar to those of extant scorpions with stacked thin sheets which have ribbed surfaces.