NGC 936, an SB0 galaxy from the SDSS
Lenticular galaxies are sometimes called “armless spiral galaxies.” Lenticular galaxies have a central bulge, but no spiral arms. If the central bulge is not very bright, it can be very difficult to tell the difference between a lenticular galaxy and an E0 galaxy.
Just like spiral galaxies, some lenticular galaxies have a bar. They are called “barred lenticular galaxies” and are denoted SB0. Normal lenticular galaxies are denoted S0.