It has 12 pentagonal faces, and 30 edges, which intersect in fives to form 12 vertices.
Quite different is the character of the pentagonal space comprised between the Gulfs of Bothnia and Finland, Lake Ladoga, and the above-mentioned line traced through the lakes Ulea and Piellis.
The keep was added to the castle in the reign of Henry I., and in the reign of Elizabeth, when the Spanish Armada was expected, it was surrounded by an elaborate pentagonal fortification.
The meeting of the coxae of all the prosomatic limbs in front of the pentagonal sternum; the space for a genital operculum; the pair of pectens, and the absence of any evidence of pulmonary stigmata are noticeable in this specimen.
Five equilateral triangles covertically placed would stand on a pentagonal base, and it was found that, by forming several sets of such pyramids, a solid could be obtained which had zo triangular faces, which met in pairs to form 30 edges, and in fives to form 12 vertices.
Dismantled since 1816, and now largely converted into promenades, the fortifications give the city an irregular pentagonal contour, modified at the north-west corner by the addition of a citadel also pentagonal.
The castle of San Fernando, r m.N.W., is an irregular pentagonal structure, built by order of Ferdinand VI.
According to his view, all mountain ranges parallel to the same great circle of the earth are of strictly contemporaneous origin, and between the great circles a relation of symmetry exists in the form of a pentagonal reseau.
Once the identity of the chilaria with the pentagonal sternal plate of the scorpion is recognized - an identification first insisted on by Lankester - the whole series of segments and appendages in the two animals, Limulus and Scorpio, are seen to correspond most closely, segment for segment, with one another (see figs.
In crystallography the icosahedron is a possible form, but it has not been observed; it is closely simulated by a combination of the octahedron and pentagonal dodecahedron, which has twenty triangular faces, but only eight are equilateral, the remaining twelve being isosceles (see Crystallography).