NGC 4651's recessional velocity of 805 km/sec is too small to be a reliable indicator of distance, as its peculiar (non-Hubble-expansion) velocity may be a substantial fraction of the measured value. And in fact, the corresponding distance of 37 million light years is considerable smaller than redshift-independent distance estimates of 50 to 100 million light years. Using the larger distance estimates, the galaxy's apparent size of 4.0 by 2.6 arcmins corresponds to 60 to 100 thousand light years (this does not include the extended arms visible in the wide-field image below).

Per Dreyer, NGC 4656 (= John Herschel's GC 3189, 1860 RA 12 37 09, NPD 57 04.0) is "remarkable, pretty bright, large, very much extended 34°, southwestern of 2". The position precesses to RA 12 43 58.3, within 0.2 arcmin of the center of the galaxy, and exactly as described (though see NGC 4657 for an explanation of "the southwestern of 2"), so the identification is certain. Based on recessional velocity of 645 km/sec, about 29 million light years away, in good agreement with redshift-independent distance estimate of 18 to 24 million light years. Given that and an apparent size of 12 arcmin (not counting faint extensions to the northeast and southwest), about 75 thousand light years across. A gravitationally bound companion of NGC 4631, which lies about half a degree to the northwest (and depending upon its distance, could be within half a million light years of its neighbor). Their interaction is probably responsible for the curved end of the galaxy (which is listed as NGC 4657), and its jocular appellation.

Per Dreyer, NGC 4657 (= John Herschel's GC 3190, 1860 RA 12 37 18, NPD 57 00.8) is "remarkable, pretty faint, large, extended about 90°, northeastern of 2". The position precesses to RA 12 44 07.1, Dec +32 13 10, about 0.6 arcmin north of the object, which is a region of bright starclouds on the northeastern end of NGC 4656, making that galaxy the 'southwestern of 2' (per its historical description) and NGC 4657 the 'northeastern of 2', confirming its identification. Though treated as a separate nebula when only the brighter portions of NGC 4656 were observable, and still listed as an irregular galaxy in some places (for instance, Steinicke lists it as a peculiar irregular), it is almost certainly a "starburst" region filled with clouds of bright stars as a result of the gravitational interaction of NGC 4656 and NGC 4631, which is less than half a degree to the northwest, and may be less than half a million light years away from NGC 4656. At the 25 to 30 million light years' distance of NGC 4656, the apparent size of NGC 4657 (about 2 by 1 arcmin) corresponds to about 7 or 8 thousand light years.

See NGC 4664 for images

Herschel observed the two galaxies as a single "possibly bi-nuclear" nebula, while Spitaler observed them as separate objects, leading Dreyer to give the separate nebulae individual IC listings, despite their already being cataloged as Herschel's NGC listing. The "Mice", so-called because of their long "tails", are a pair of interacting galaxies about 300 million light years away. The two galaxies have recently collided with each other, and will continue to do so again and again (over periods of hundreds of millions of years), until they eventually merge into a single galaxy. In the meantime, their gravitational interaction pulls stars away from each galaxy to form their elongated tails, and compresses the gas and dust between the stars, forming associations and clusters of hot, bright young stars which heat and light up the clouds out of which they just formed.

Based on a recessional velocity of 6790 km/sec, NGC 4685 is about 315 million light years away. Given that and its apparent size of 1.6 by 1.0 arcmin, the main body of the galaxy is about 150 thousand light years across. It also has extended "arms" which cover an additional 40 thousand light years both north and south of the central structure. NED lists NGC 4685 as a member of a group (M98j 181). Its distorted appearance is probably due to gravitational interactions with other members of the group.

A member of the Virgo cluster of galaxies. Based on a recessional velocity of 1240 km/sec, NGC 4697 is about 58 million light years away, in good agreement with redshift-independent distance estimates of 30 to 75 million light years. Given that and its apparent size of 7.2 by 4.7 arcmins, the galaxy is about 120 thousand light years across.