wards, about 0.8 mm. long, with prominent lateral arms. 
Stigmas on the lateral arms confluent below the rostel- 
lum. All parts of the flower pale greenish yellow. 
Mexico: San Juan Lalana (near Santiago Choapam), long. 95°45’, 
lat. 17°25’, District of Choapam, Oaxaca, at about 1900 feet (about 
600 meters) altitude, May 7, 1939, Richard Evans Schultes & Blas Pablo 
Reko 805 (Tyrenin Herb. Ames No. 57280; Isoryprs in Herb. Inst. Bi- 
ologia (Chapultepec, Mexico), in Herb. Field Museum, in Herb. 
Halbinger and in Herb. Schultes). 
I take great pleasure in naming this new species of 
Pleurothallis in honor of Mr. Christian Halbinger, in 
recognition of his interest in the furtherance of the study 
of Mexican Orchidaceae and in grateful appreciation of 
the help which he has given me during my botanical 
trips in Mexico. 
Pleurothallis Halbingeriana is closely allied to P. 
propinqua Ames of Costa Rica and to P. lancilabris 
(Reichb.f.) Schltr. of Costa Rica and southern Mexico. 
Pleurothallis Halbingeriana agrees with P.propinqua 
in general floral structure, but the latter is much larger 
than the former in all its parts. Furthermore, P. propin- 
qua has oblanceolate or spatulate leaves which are bilob- 
ulate at the apex and peduncles which only slightly 
overtop the leaves, whereas P. Halbingeriana has ellip- 
tical leaves which are strongly mucronate at the apex and 
peduncles which conspicuously overtop the leaves. Minor 
floral differences further separate these two species. The 
relationship between them, however, is extremely close. 
Pleurothallis lancilabris, which Ames regards as a close 
ally of P. propinqua, is related to P. Halbingeriana; but 
the relationship is more remote than that between P. 
propinqua and P. Halbingeriana. Although vegetatively 
rather similar to P. Halbingeriana, P.lancilabris differs 
in having linear (not lanceolate) petals and very long- 
acuminate (not short-acuminate) sepals. Furthermore, the 
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