How do the gill openings of Myxinidae differ from those of Eptatretinae hagfishes?

In the classification of hagfishes, the gill openings differ significantly between the two subfamilies of the family Myxinidae:

• Subfamily Eptatretinae: These hagfishes possess 5 to 15 pairs of gills that open separately to the outside surface of the body.12
• Subfamily Myxininae: In these species, the 5 to 7 pairs of gills do not open directly to the surface. Instead, they open internally into collecting ducts, which then lead to the outside through a single pore on each side.1

While some classifications occasionally group these into separate families (Myxinidae and Eptatretidae), the distinction in their respiratory anatomy remains consistent regarding whether the gill pairs share a common exit or open individually.2