A lollipop tang ends in a circle at the last screw, just in front of the comb. It is shaped like a lollipop, hence the name.
Hlbly is correct in his description of a lollipop tang and you will see them on many later Gillespie rifles. I also have seen several Gillespie's that used a slightly modified version of the standard lollipop tang. Here is a photo of one that is on one of Harvey Gillespie's rifles.
As a side note, I have also heard the lollipop tangs referred to as doll's head tangs.
(https://americanlongrifles.org/forum/proxy.php?request=http%3A%2F%2Fimage.ibb.co%2Fj19OQv%2Ftang.jpg&hash=4242ad2f25c5fa451b54d5cc3092b4a008bb5d9a) (http://ibb.co/niCckv)
I saw one with a more pronounced valentine shape instead of the normal round circle but I do not have a photo of that one.
online print screen (http://imgbb.com/)