We present B and V CCD aperture photometry for a morphologically-selected sample of forty-nine southern , extreme late-type spiral galaxies .
All objects are moderate-to-low surface brightness Local Supercluster field galaxies that were detected previously in H i surveys .
Our sample features objects that have optical luminosities , optical sizes , and H i masses which are at the low end for spiral galaxies .
These objects are not a new class of galaxy , but are examples of a common type of spiral galaxy that has been under-represented in nearby galaxy samples .

We discuss the limitations of standard photometric techniques as applied to extreme late-type spirals , and adopt a simple method of characterizing the light distributions of such objects in terms of aperture magnitudes , colors , color gradients , “ mean disk scales ” , and optical structure .

In many respects , the global properties of extreme late-type spirals are intermediate between irregulars and ordinary high surface brightness spiral galaxies .
While our sample galaxies generally have regular structures and well-defined centers , some of the objects are very blue and/or have large gas fractions ( \frac { { \cal M } _ { HI } } { L _ { V } } \sim 3-9 ) —i.e .
properties which have been traditionally associated with dwarf irregular galaxies .
Several galaxies become redder with increasing radius , a trend which seems to be uniquely found in certain dwarf and very late-type disk galaxies .
In addition , we find bars to be common in extreme late-type spirals .

Our sample exhibits a diverse array of structural properties and morphologies in galaxies with otherwise similar physical parameters ( e.g. , M _ { B } , { \cal M } _ { HI } , B–V ) .
A number of the galaxies possess unresolved , point-like nuclei which may be related to low-luminosity AGNs or to M33-like compact nuclei .
Finally , several of the galaxies show distinctive surface brightness “ steps ” in their disks , demonstrating that even small , late-type spirals can have multi-component disks .