  Abstract Theoretical framework is developed that explains biskyrmion lattices
observed in non-chiral magnetic films. We study films of finite thickness
containing up to $1000\times1000\times100$ spins. Hexatic biskyrmion lattices
in a pure 2D exchange model are naturally described by the Weierstrass $\wp$
and $\zeta$ elliptic functions. Starting with such a lattice as an initial
state we investigate how it evolves towards the minimum-energy state in the
presence of perpendicular magnetic anisotropy and dipole-dipole interaction. In
accordance with experiments, we find that the final state is a triangular
lattice of biskyrmion bubbles containing Bloch lines.
