B

banner— Upper petal of a pealike flower. (See Fig. 6.1.)

basalt— A general term for a dark-colored igneous rock, commonly extrusive but locally as intrusive dikes (tubular igneous intrusions).

Basin and Range— Geomorphic province in eastern California and western Nevada; topography or landscape characterized by a series of tilted fault blocks.

biomass— The total mass or amount of living organisms in a particular area or volume.

biotite— Widely distributed rock-forming mineral of the mica group; layer-structure silicate containing essential potash, iron, magnesia, alumina, and H₂ O in addition to silica; a typical formula is K(Mg, Fe⁺² )₃ (Al, Fe⁺³ )Si₃ O₁₀ (OH)₂ .

bioturbated— Refers to sedimentary rocks that have been churned and stirred by organisms.

bipedal— Using two legs for locomotion.

boss— A swollen bump on the heads of certain toads.

bract— A reduced leaf subtending a flower, usually associated with an inflorescence.

breastwork— A small, curved rock wall, commonly used as a hunting blind.

buff— Medium to dark tan.

burred phrases— A trilled sequence of rough or gutteral sounds.

bursa— A small outpocketing or sac near the end of the digestive tube in a young bird.