Octadecagon Octadecagon An octadecagon (or octakaidecagon) or 18-gon is an eighteen-sided polygon. A "regular octadecagon" has a Schläfli symbol {18} and can be constructed as a quasiregular truncated enneagon, t{9}, which alternates two types of edges. As 18 = 2 × 3, a regular octadecagon cannot be constructed using a compass and straightedge. However, it is constructible using neusis, or an angle trisection with a tomahawk. The following approximate construction is very similar to that of the enneagon, as an octadecagon can be constructed as a truncated enneagon. It is also feasible with exclusive use of compass and straightedge. The "regular
Many-finned sea serpent Wake of Bernard Heuvelmans" that the evidence points towards an invertebrate rather than a cetacean identity, and has speculated that the con-rit might be a fully aquatic descendent of the giant myriapod "Arthropleura", which became extinct at the beginning of the Permian period. He has also suggested an alternative to Heuvelman's original binomial name for it in the form of "Mariascolpendra aelani" (Woodley, 2007), which translates as 'Aelian's sea centipede'. Many-finned sea serpent The many-finned sea serpent is an unverified species or group of species of marine animals which seem to possess numerous fins along their sides or backs. The