We present the results of the spectroscopic and photometric follow-up of two field galaxies that were selected as possible stellar counterparts of local high velocity clouds . Our analysis shows that the two systems are distant ( D > 20 Mpc ) dwarf irregular galaxies unrelated to the local H I clouds . However , the newly derived distance and structural parameters reveal that the two galaxies have luminosities and effective radii very similar to the recently identified ultra diffuse galaxies ( UDGs ) . At odds with classical UDGs , they are remarkably isolated , having no known giant galaxy within \sim 2.0 Mpc . Moreover , one of them has a very high gas content compared to galaxies of similar stellar mass , with a H I to stellar mass ratio M _ { HI } / M _ { \star } \sim 90 , typical of almost-dark dwarfs . Expanding on this finding , we show that extended dwarf irregulars overlap the distribution of UDGs in the M _ { V } vs. log r _ { e } plane and that the sequence including dwarf spheroidals , dwarf irregulars and UDGs appears as continuously populated in this plane . This may suggest an evolutionary link between dwarf irregulars and UDGs .