Using the Tremaine-Weinberg method , we measure the speed of the HI bar seen in the disk of NGC 3741 .
NGC 3741 is an extremely gas rich galaxy with an H i disk which extends to about 8.3 times its Holmberg radius .
It is also highly dark matter-dominated .
Our calculated value of the pattern speed \Omega _ { p } is 17.1 \pm 3.4 km \textrm { s } ^ { -1 } \textrm { kpc } ^ { -1 } .
We also find the ratio of the co-rotation radius to the bar semi-major axis to be ( 1.6 \pm 0.3 ) , indicating a slow bar .
This is consistent with bar models in which dynamical friction results in a slow bar in dark matter dominated galaxies .