The Pyramidalis is a very small triangular shaped muscle that originates off the pubic crest. Its function is to tense the linea alba. The line alba is the line in the rectus abdominis.
Fascially, this muscle I believe holds important tension relationships between the adductor fascia and the abdominal fascia.
It is essentially a crossroads between the opposite adductor and the opposite oblique muscles. This is sometimes referred as the anterior oblique system.
Find your belly button. Slowly palpate lower until you hit bone. You will be on the pubic crest. Slowly rub back and forth. One side is usually more tender. This would be the one to target. This muscle can play a contributing factor to pubic area pain, abdominal pain and groin pain. Hockey and soccer players will often present with this.
I usually have the patient or athlete do this on their own as it's in a pretty sensitive area.