rbeesley.nospam@gmail.com wrote:
....

> head
> and tail are clearly concatted (is that a word?)


FWIW, and only since you asked: it's "concatenated".

NSOED says:

concatenate /kn"katIneIt/ v.t.

L16. [Late L concatenat- pa. ppl stem of concatenare, f. as
CON- + catena CHAIN n.: see -ATE3.]

Link together (chiefly fig.); connect as by a chain.