Halton Arp's "Atlas of Peculiar Galaxies" was meant to provide examples of various types of galaxies as a guide for study of the origin and evolution of galaxies, at a time (the mid-1960's) when astronomers had little idea what that involved. Although the Atlas was intended only as a sampling, rather than an inclusive listing of galaxies, it contains a number of interesting objects that are often referred to by their Arp numbers. The table below is based on Arp's description of each "group" of catalog entries. For each entry a thumbnail image, its Arp number, and a "standard" catalog identification is shown; a plus sign indicates that more than one object is part of the Arp listing. To see a detailed discussion and better images of an Arp object, click on its Arp designation or thumbnail image.