We compare the transverse velocity dispersions recently measured within the Sculptor dwarf spheroidal galaxy to the predictions of previously published dynamical models .
These provide good fits to the observed number count and velocity dispersion profiles of metal-rich and metal-poor stars both in cored and in cusped potentials .
At the projected radius where the proper motions were measured , these models predict transverse dispersions in the range 6 to 9.5 km/s , with the tangential dispersion about 1 km/s larger than the ( projected ) radial dispersion .
Both dispersions are predicted to be about 1 km/s larger for metal-poor than for metal-rich stars .
At this projected radius , cored and cusped potentials predict almost identical transverse dispersions .
The measured tangential dispersion ( 8.5 \pm 3.2 km/s ) agrees remarkably well with these predictions , while the measured radial dispersion ( 11.5 \pm 4.3 km/s ) differs only at about the 1 \sigma level .
Thus , the proper motion data are in excellent agreement with previous data but do not help to distinguish between cored and cusped potentials .
This will require velocity dispersion data ( either from proper motions or from radial velocities ) with uncertainties well below 1 km/s over a range of projected radii .