From this article in Car Craft:
http://carcraft.com/techarticles/116_0410_hemi/
it is clear that the new "Hemi" does indeed have what is known as a hemispherical combustion chamber but with added squish zones on the edges thus combining the best of the cross-flow design with the squish/quench zones of a wedge! Not only that but it is a twin spark to boot!
Also, as far as I understand it valve overlap does help to suck the mixture in...