HORSE RACE (or HORSE TAIL)
Longways whole set for as many as will, from Bill Martin
Old-timey music, not too deeply concerned with phrasing.  (It takes a 
bit longer depending on how many people in the set).

A1: Lines F&B; again
A2: partners do-si-do
B1: partners allemande right; then left
B2: Horse race!  
    Top couple arches over men's line (man outside) while
    next couples arches over women's line (woman outside);
    they skip down to the bottom and up the other side, and it's 
    up to them to work out how they pass the other arching couple.
    When you get back to the top, gallop down the middle to the bottom
    and stay there; the dance starts again.
    

Bill Martin's descriptions:

Neigh-h-h-h! Oh, now Dudley, don't get your hopes up. Its a dance I
call "Horserace", a variation on all the other variations. I don't
know where I got the horseracing part of the dance. Its a longways
whole set dance. What I usually do is long lines up and back a couple
of times, do-si-doz and allemandes and such, and then... the two top
couples race each other. First couple makes an arch over one line,
skipping to the bottom and then back to the top over the other line.
At the same time the second couple does the same, going first over the
line that the first couple ain't. They have to get by each other as
politely or viscously as possible. As soon as they get to the top they
keep sashaying down the center to the bottom, where they stay. Dance
starts again. I always get amused when I call it for a mixed age group
because the adults really get competitive, shutting down the little
tykes and stomping them flat. They should be ashamed.

Bill Martin