2. (Crystallog.)
Defn: Same as Tetragonal. Pyramidal numbers (Math.), certain series of figurate numbers expressing the number of balls or points that may be arranged in the form of pyramids. Thus 1, 4, 10, 20, 35, etc., are trangular pyramidal numbers; and 1, 5, 14, 30, 55, etc., are square pyramidal numbers.
PYRAMIDAL
Py*ram"i*dal, n. (Anat.)
Defn: One of the carpal bones. See Cuneiform, n., 2 (b).
PYRAMIDALLY
Py*ram"i*dal*ly, adv.
Defn: Like a pyramid.
PYRAMIDIC; PYRAMIDICAL
Pyr`a*mid"ic, Pyr`a*mid"ic*al, a.
Defn: Of or pertaining to a pyramid; having the form of a pyramid;
pyramidal. " A pyramidical rock." Goldsmith. "Gold in pyramidic
plenty piled." Shenstone.
— Pyr`a*mid"ic*al*ly, adv. Pyr`a*mild"ic*al*ness, n.
PYRAMIDION
Pyr`a*mid"i*on, n.; pl. Pyramidia. Etym: [NL., from L. pyramis. See
Pyramid.]
Defn: The small pyramid which crowns or completes an obelisk.