without through the lower half. Lateral sepals falcate- 
decurved, 8.5—9 mm. long, connate into an elliptic-ovate 
bilobed lamina about 5 mm. wide which is 6-nerved, bi- 
carinate without below the middle and finely pubescent 
within and on the margins (except near the base), form- 
ing a prominent mentum with the column-foot, the apex 
of the sepals is subacute. Petals smaller than the sepals, 
falcate-spatulate, about 6.3 mm. long, 2.8-3 mm. wide, 
broadly rounded above, 8-nerved in the middle with the 
center thickened above the nerves. Lip strongly arcuate 
in natural position with the sides of the dilated median 
portion incurved; when expanded about 6.5 mm. long, 3- 
nerved, from a narrow elongate claw-like portion rather 
abruptly semiovate-dilated on each side (about 2.2 mm. 
across), then gradually narrowed into an oblong apically 
rounded lamina which is slightly longer than the basal 
portion, denticulate on the apical margins, with the sur- 
face of the apical portion irregularly papillose; a low 
intramarginal keel extends from the lower part of the 
dilated portion on each side nearly to the apex. Column 
slender, dilated below, arcuate, about 4 mm. long at the 
back, slenderly winged with a cucullate apex, provided 
with a prominent foot. 
Pleurothalls dilatata differs from the similar P. trilin- 
eata Lindl. in having eciliate floral bracts, connate lat- 
eral sepals and a more slender lip. It varies from P. 
asperilinguis Reichb.f. in having broader sepals, obtuse 
petals and a narrower lip. 
The specific name is in allusion to the dilated middle 
portion of the lip. 
Huancavetica: Prov. Tayacaja, Montepungo, 5 kilometers east of 
Surcubamba, at 3000 meters altitude, epiphyte on mossy tree trunk, 
flower pale greenish yellow, January 13, 1939, H. E. Stork & O. B. 
Horton 10388. (Tyrer in Herb. Univ. Calif.). 
[178 ] 
