Cast on 25 (29, 33) sts. Beg with a purl row, work 5 St st rows. Inc 1 st each edge now and then every 4th row twice more -- 31 (35, 39) sts. Work even to approx 2 1/2 (3, 3 1/2) inches from beg, ending with a WS row.
Row 1 (RS): K15 (17, 19) sts, pm, M1, k1, M1, pm, k15 (17, 19).
Row 2: Purl.
Row 3: K to marker, sl marker, M1, k to marker, M1, sl marker, k to end of row.
Rep Rows 2-3 until there are 13 (13, 15) sts between markers. Purl next row, removing markers. Next Row: K across, placing thumb sts onto a spare strand of yarn. Work even on the 30 (34, 38) sts until piece measures approx 8 1/2 (9, 9 1/2) inches from beg, ending with a WS row and pm after 15th (17th, 19th) st.
Dec Row (RS): Ssk, k to 2 sts before marker, k2tog, sl marker, ssk, k to last 2 sts, k2tog. Next Row: Purl. Rep last 2 rows until 18 (18, 22) sts rem. On next RS row, (k2tog) across. P9 (9, 10). Leaving a long tail for sewing, cut yarn.
Thread tail into yarn needle. Beg with the last st on needle, take yarn back through rem sts, twice. Pull up to tightly close opening. Join sides tog.
With RS facing, return sts to needle. Join yarn and k13 (13, 15). Next Row: P5 (5, 7), p2tog, p6. Work 6 (6, 8) more St st rows on the 12 (12, 14) sts. Next Row: (K2tog) across. Cut yarn, leaving a 10 inches tail. Rep Closure as for Top. Join thumb seam. Darn opening. Weave in loose ends on WS of fabric.
Work as for First Mitten.