According to the "Catalog of Cometary Orbits", compiled by Dr. Brian Marsden at the Harvard/Smithsonian Center for Astrophysics, there have been several comets with that name:
1957 V Comet Myrkos 1959 IX Comet Myrkos 1962 I P/Perrine-Myrkos 1964 VII P/Honda-Myrkos-Pajdusakovaduring the period from 1957-1965, but only 1957 V was a spectacular naked-eye comet. It was discovered on August 2, 1957 under rather amusing circumstances. The bright comet Arend-Roland had just finished a spectacular display in the sky a month earlier, and was fading rapidly. Comet Myrkos was discovered in practically the same part of the sky, so that some observers were caught off guard. It is reported in IAU Circular 1616, and Sky and Telescope offers some very spectacular photos of it in their October, 1957 issue. The orbital elements for this comet are:
T August 1.44 (UT) q 0.35 AU w 40.3 degrees W 215.2 degrees i 119.9 degrees P > 200 years e 0.9994
The photos show its tail split into two components which is the classic situation for many comets. Comet Myrkos is often used to illustrate the canonical features of cometary tail composition and dynamics. One tail, the more diffuse component, is the dust being shed by the comet along its orbit, illuminated by scattered light from the sun. It changes very little in appearance due to any internal dynamics of the comet. The second tail is much sharper and consists of ionized gas shed by the comet's nucleus. This plasma interacts with the solar wind and the solar magnetic field in interplanetary space. A consequence of this interaction is that the ion tail changes its appearance almost hourly as plasma instabilities grow and subside forming fluted shapes and waves that travel from the head of the comet, outward into the far tail region.