The use of natural spectral-form groups (Morgan, 1951) on low-dispersion slitless survey plates efficiently isolates rather pure samples of intrinsically interesting extragalactic objects (e.g. Smith, 1975, 1976; Smith, Aguirre and Zemelman 1976; MacAlpine, Smith and Lewis 1977a, b; MacAlpine, Lewis and Smith 1977, MacAlpine and Lewis 1978, Cooke et al. 1977, Hoag and Smith 1977, Sramek and Weedman 1978, Bohuski, Fairall and Weedman 1978, Osmer and Smith 1979). One of these groups (illustrated for various telescopes by Smith 1975, Hoag and Smith 1977, Bolton et al. 1977 and Smith 1978) has been found to include a very large set of high-redshift QSOs. Definition of the group (e.g. Smith 1976) rests on the direct detection of the QSO emission lines on the survey plates. Objects already selected from the group range in redshift from 0.32 (PKS 2227-399 - see also Peterson and Bolton 1978, Browne, Savage and Bolton 1976, Bolton et al. 1977) to 3.45 (Q2227-6-3928 - Smith et al. 1977, Osmer 1978a) and in apparent magnitude from 21 (Osmer 1977, Smith 1978) to 16 (including the apparently brightest high-redshift object known, Q1101-264). - Osmer and Smith 1976, Smith 1978, Carswell et al. 1979 and the most luminous object known, Q0420-388 -Osmer and Smith 1977b; Wright and Kleinmann 1978). 15 of the 21 objects known with confirmed redshifts z > 3 have been discovered this way.