horseshoe crab

(multiple of 12 sts plus 3)
Row 1 (RS) K1, k2tog, yo, *k2, yo, k1, sl 1-k2tog-psso, k1, yo, k2, yo, sl 1-k2tog-psso, yo; rep from * to last 12 sts, k2, yo, k1, sl 1-k2tog-psso, k1, yo, k2, yo, SKP, k1.
Row 2 Purl.
Row 3 K1, k2tog, yo, *k3, yo, sl 1-k2tog-psso, yo; rep from * to last 6 sts , k3, yo, SKP, k1.
Row 4 Purl.
Rep rows 1-4.