With 2 strands of yarn held tog, ch 38.
Row 1: Sc in 2nd ch from hook and each ch across – 37 sts.
Row 2: Ch 1, turn. Sc in each st across.
Rep Row 2 until piece measures about 12 in. (30.5 cm) from beg.
Next Row: Ch 4 (counts as 1st tr), sk next sc, work 1 tr in next sc, * skip 4 sc, (tr, ch 1, tr, ch 1, tr, ch 1, tr) in next st – Shell made; rep from * across, end last rep skip 4 sc, 2 tr in last sc.
Next Row: Ch 4, turn. Skip next tr, tr in next tr, *work Shell in center ch-1 space of Shell; rep from * across, end 2 trc in last tr.
Rep last row until piece measures about 17 in. (43 cm) from beg.
Fold lower edge of bag up about 6 in. (15 cm), and seam sides. Sew on button. Weave in ends.