These are listed by Common  name.  They are in the genus "Pelargonium".  The perennial geranium is in the genus "Geranium".  Confusing, huh?  That's why we try to use the botanical names.  Anyway, the first section is P. peltatum (Ivy Geraniums).  The next ones down the list are P. x hortorum (zonal geraniums).