The determination of the maximal packing arrangements of two-dimensional, binary hard disks of radii RS and RL (with RS 6 RL) for su ciently small RS amounts to ÿnding the optimal arrangement of the small disks within a tricusp: the nonconvex cavity between three close-packed large disks. We present a particle-growth Monte Carlo algorithm for the generation of geometric packings of equi-sized hard disks within such a tricusp. The ÿrst 19 members of an inÿnite sequence of maximal density structures thus produced are reported. In addition, the Monte Carlo algorithm is applied to the geometric packing of disks within a at-sided equilateral triangle and compared to published results for that packing problem. We perform an analysis of geometric properties of the packings, e.g. packing fractions and symmetries of structures conÿned to both containers. Interestingly, we ÿnd a non-monotonic increase in the packing fraction with increasing number of disks packed within both the at-sided triangle and tricusp. It is important to note that for disk packings within a at-sided equilateral triangle, this non-monotonic behavior of the packing fraction had not been reported in previously published works. For the at-sided equilateral triangle, local maxima occur at the triangular integers NS =1; 3; 6; 10; 15 : : : ; as well as NS = 12; where NS is the number of disks in each packing. However, local maxima for packings within the tricusp exist at NS = 1; 3; 6; 10; 18 : : : : Finally, we analyze the asymptotic approach to the upper bound on the packing fraction of the inÿnite sequence of maximal structures of disks conÿned to the tricusp.