I have found sources claiming as such, but none authoritative.
Although the structure resembles a placental mammal's scrotum, one cannot assume.
However, I am curious to find out what exactly it is since it seems oddly placed anatomically.
The following is a link to a baby echidna (puggle) at the Taronga Zoo; hopefully you will see what I am referring to.
http://youtu.be/SGleaTJoy1U?t=34s
