Culmen

"the Shibboleth and Culmen of Honesty"

"The measurements were taken as follows: wing length, from the carpal joint to the tip of the longest primary; tarsus length, from the tibiotarsal joint to the distal undivided scute; upper mandible length, the chord length from the point where the culmen enters the feathers of the head to the tip; bill depth, in the vertical plane level at the anterior edge of the nares."