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abstract. Two new species of Pleurothallis subsection Macrophyllae-Fasciculatae from Costa Rica, allied to P. cardiothallis, are described and illustrated, and their relationships discussed. Pleurothallis scotinantha is compared with P. oncoglossa, from which it can be easily distinguished by the concolorous, dark purple flowers, the distinctly deflexed petals, and the lip without a distal callus that is not hooked at the apex. Pleurothallis navisepala, from the northern Costa Rican cordilleras, is compared with P. cardiothallis, from which it is distinguished by the simultaneous flowering of two or more flowers, the much smaller size of the flowers, and the deeply navicular sysnsepal, which prevents complete spreading of the flower. A key to the Costa Rican species of the group is presented. Observations on floral behavior in the species allied to P. cardiothallis are provided and the possible function of this behavior is discussed. The visit of a tephritid fly to the flowers of P. navisepala is described.

abstract. Two new species of Pleurothallis subsection Macrophyllae-Fasciculatae from Costa Rica are described and illustrated, and their relationships discussed. Pleurothallis pudica, from the central Pacific mountain region, is compared with P. phyllocardia, but it is easily recognized by the densely pubescenthirsute flowers. Pleurothallis luna-crescens, from the Caribbean slope of the Talamanca chain, is compared with P. radula and P. rectipetala, from which it is distinguished by the dark purple flowers and the distinctly longer, dentate petals, respectively. A key to the species of the group in Costa Rica and western Panama is presented.