Fig. 4 in Enrolment in a Middle Ordovician agnostoid trilobite

Fig. 4. Trinodus elspethi (Raymond, 1925), silicified specimens from Edinburg Formation, Virginia, USA. A. PMO 206.303. Cephalon in posterior (A1), tilted frontal (A2), and oblique lateral (A3) views from ventral. Note hollow posterolateral spine. B. PMO 206.307. Completely enrolled specimen; B1, ventral view, note cephalothoracic aperture is not visible and how the second thoracic segment overlaps the pygidium at the shoulder; B2, oblique posterior view showing cephalothoracic aperture and how distal tip of first thoracic segment slots into base of posterolateral spine; B3, specimen tilted from ventral position so that cephalothoracic aperture is visible; B4, detail of articulation between cephalon and first thoracic segment. C. PMO 206.306/2. Posterior view of pygidium to show raised flange of doublure.