SS in crochet?? Need help

I have a crochet pattern from the Bernat website. It is for a crochet baby shawl.
On the 6th row it begins with: ss in first dc. I checked their abbrev. section and could not find what ss means. I looked on cyca and can not find this abbrev. here. Does anyone know what this stands for?? It doesn't mean slip stitch. Sl st is the abbrev. for slip stitch. Your help would be greatly appreciated.

Thank you