  We have used the ROSAT Bright Source Catalogue to extract a complete sample
of sources selected in the band from 0.1-0.4 keV. This 1/4 keV-selected sample
is comprised of 54 Seyfert galaxies, 25 BL Lacertae objects, 4 clusters and 27
Galactic stars or binaries. Seyfert-type galaxies with ``ultrasoft'' X-ray
spectra can very often be classed optically as Narrow-line Seyfert 1s (NLS1s).
Such objects are readily detected in 1/4 keV surveys; the sample reported here
contains 20 NLS1s, corresponding to a 40% fraction of the Seyferts. Optical
spectra of the Seyfert galaxies were gathered for correlative analysis, which
confirmed the well-known relations between X-ray slope and optical spectral
properties (e.g., [O III]/H-beta ratio; Fe II strength, H-beta width). The
various intercorrelations are most likely driven, fundamentally, by the shape
of the photoionising continuum in Seyfert nuclei. We argue that a steep X-ray
spectrum is a better indicator of an ``extreme'' set of physical properties in
Seyfert galaxies than is the narrowness of the optical H-beta line. (Abridged)
