Nereocaris exilis gen. et sp. nov. from the Cambrian (Stage 3) of British Columbia. (a) Holotype, Royal Ontario Museum (ROM) 61831. (b) Paratype ROM 61832. (c) Paratype ROM 61833. (d) Details of ocular region located in top box of (c), immersed in water. (e) Details of the appendicular region located in box of (a). (f) Details of the posterior part of the gut located in the posterior box of (c), showing three-dimensional preservation. All specimens were photographed using low-angle cross-polarized light. Accompanying camera lucida drawings in electronic supplementary material S1, figure S1. ah, anterior hook-like processes; as1–62, abdominal somites 1–62; cs, corneal surface; dk, dorsal keel; en, endopod; ep, eye peduncle; ex, exopod; fl, fluke; gut, gut; le, lateral eyes; ltp1–3, lateral telson processes 1–3; lv, left valve; mg, midgut glands; mtp, medial telson process; pm, photoreceptive material; sf, setal fringe; ts, thoracic segments.