Pomona College, Claremont, California 53 
a similar patch, though less conspicuous. Another related but dis- 
tinct species is O. sancta-rose. 
Habitat: Mountains near Claremont, California (Baker; 
Pomona coll. 182, part). This may be a southern subspecies of 
O. tristella. 
A totally different Osmia from Claremont (Baker), marked 182, 
is O. novomewxicana Ckll., with the hair of the thorax above less 
brightly colored than in New Mexico specimens, but otherwise iden- 
tical. 
Osmia nigrobarbata sp. n. 
2 Length a little over 10 mm.; robust; head, mesothorax and 
scutellum dark green; pleura and metathorax much bluer; abdomen 
shining greenish-blue; legs black, without metallic tints; head broad; 
eyes pea-green; mandibles tridentate, the teeth very large; clypeus 
black (except borders), with dense coarse black hair, contrasting 
with pure white hair on sides of face; front and vertex with hair 
mixed black and white; upper part of cheeks with white hair, lower 
with more or less black; flagellum short, very obscurely reddish 
beneath; mesothorax and scutellum with extremely dense small 
punctures; area of metathorax shining except basally; mesothorax 
with thin white hair, with some black intermixed; tubercles with 
pale hair, but pleura with black; scutellum with abundant creamy 
hair, a few black intermixed; metathorax with black hair on lower 
part of sides, otherwise with pale; legs with black hair, more or 
less brownish on tarsi, a small tuft of pure white on posterior knees; 
tegule black, green in front; wings brownish, especially the broad 
apical margin; first r. n. joining second s. m. at a distance from 
its base equal to length of first t. c.; abdomen with white hair on 
first segment, scanty black hair beyond, but grayish-white on sixth 
and apical margin of fifth; scopa black. 
Habitat: Claremont, California (Baker; Pomona coll. 182, 
part). Easily known by the contrasting black and white hair on 
face. It resembles O. senior Ckll., but differs by the shining area of 
metathorax, tridentate mandibles with large teeth, etc. 
Osmia melanopleura sp. n. 
? Length about 7.5 mm.; dark blue-green, densely punctured 
but somewhat shining; facial quadrangle longer than broad; mandi- 
