Class is an outdated notion. If you are in the same subnet, then it is not going out on the internet. With the information you've provided, it's impossible to tell whether this is the case. I assume that the majority of your subnet mask is 255. If you post your subnet mask and the parts of your IP addresses corresponding to the non-255 parts of your subnet mask, then I can tell you if the two machines are on the same subnet or not, while you retain your anonymity.
BTW, the ethernet is faster than the USB in most cases, but is not orders of magnitude faster. Maybe 2-3 times. Keep in mind that it's 10BaseT, not 100BaseTX.
_________________________
Bitt Faulk