English: Arches of various forms as follows:—
2. Semicircular arch, the centre of which is in the same line with its springers.
4. Horseshoe arch, with the centre above the springing; employed in Moorish architecture.
6. Equilateral pointed arches, described from two centres, the radius being the whole width of the arch.
8. Lancet arches, with centres outside the arch.
10. Four centre arches, employed in the Perpendicular and Tudor periods.
12. Pointed horseshoe arches, found in the mosque of Tulun, Cairo, 9th century.
14. Cusped arch; Christchurch Priory, Hants.
16. Flat arch, where the soffit is horizontal and sometimes slightly cambered (dotted line).
Illustration from 1911 Encyclopædia Britannica, article Arch.