Washington, DC: Smithsonian Institution, 1939. Paperback. 8vo. Tan wrappers. Pp. 157-181. Line drawings, figures, tables, illustrations. Very good. Item #25865
Offprint from the 1939 "Smithsonian Report" -- NOT a disbound section, but the less-often-seen separate offprint, with handsome printed outer wrappers. Unusually early study of this topic.