Unimplemented. Similar to type A. The curve y2 = x3 + 1 over the field F_q for some prime q = 2 mod 3, which implies cube roots in F_q are easy to compute, though we can achieve this for type A pairings by constraining q appropriately. I recommend requiring q = 3 mod 4 as well, so that -1 is a quadratic nonresidue.
The lack of an x term simplifies some routines such as point doubling.
It turns out we must choose between symmetry or efficiency due to the nature of a certain optimization.