that is about 10% of total galaxy luminosity. The observed colour indexes of unrolled spiral arm ($V-R\,=\,$+0.4, $R-I\,=\,$+0.4) are more blue than colour indexes of the main galaxy. The mean colours of the pseudo-ring indicate an age of about $\rm 10^{9}$ years, for a solar metallicity. The matter of the pseudo-ring probably contains some dust since in the region of the spiral arm projection to the SW edge of main body the local increase of colour indexes (with $E_{V-R}\,=\rm\,0.^{m}1-0.^{m}15$) is observed. In addition, visual inspection of the reproduction of this system in the Atlas by Arp (1966) shows that there is some absorption in this region.

The whole projected length of twined arm ($\geq$2’$=$55 kpc) gives a possibility to estimate the duration of twisting of accreted matter around NGC 3808B. Adopting that a velocity of the gas is equal to maximum observed velocity in the forming ring (120 km/s), one can find that the duration of active phase of interaction with mass transfer is at least $\rm 4\times10^{8}$ years. Taking into account the projection factor this period may be increased up to $\rm 10^{9}$ years. This value corresponds approximately to the stellar population age in the forming ring. Therefore, in 