nerved with the mid-nerve dorsally carinate. Lateral se- 
pals connate into a deeply concave lamina which is sub- 
orbicular when expanded; lamina 4-5 mm. long, 4-4. 4 
mm. wide, acute, 4-nerved, with the inner nerves dorsally 
somewhat carinate below. Petals much smaller, oblong- 
linear, sometimes with a slightly dilated base, acute and 
incurved at the thickened apex, about 2.1—2.5 mm. long, 
up to 1 mm. wide, 1-nerved, with a prominent dorsal keel. 
Lip simple, deeply conduplicate-concave, triangular- 
ovate, with a pair of retrorse triangular-lanceolate obtuse 
auricles, about 2 mm. long in natural position, acute with 
an incurved mucronate apex; disc 8-nerved, slightly nar- 
rowed on each side below the middle, provided with a 
hippocrepiform callus at the base. Column very short 
and stout. 
Pleurothallis concaviflora is apparently allied to P. 
excavata Schitr., but has longer stems, shorter leaves, 
almost twice smaller flowers and dissimilar petals. It is 
vegetatively similar to P. Sanchot Ames, but has very 
different petals and a dissimilar lip. 
Costa Rica, ‘‘Colinas de San Pedro de San Ramon. 14-x1-1927."" 
A. M. Brenes (134) 1668 (Type in Herb. Ames No. 43774). 
Pleurothallis rotundata C. Schweinfurth sp. nov. 
Herba parvula, caespitosa. Caules monophylli, vaginis 
tubularibus hispidis cum ostiis ovatis omnino tecti. Fo- 
lum erectum, late ovale vel suborbiculare, apice basique 
rotundatum. Racemi axillares, numerosi, perbreves, bi- 
fori. Sepala anguste lanceolata vel triangulari-lanceolata, 
acuminata, lateralia per tertiam basalarem connata. Pe- 
tala perparva, oblonga, marginibus superioribus longe 
fimbriatis. Labellum lanceolatum, acuminatum, triner- 
vium, marginibus inferioribus ciliatis vel fimbriatis. 
Plant small, caespitose, up to 18 em. high to the apex 
of the erect leaf. Stems 2.2-10.1 em. tall, entirely con- 
[115 | 
