Adapted from Plate 19, Family 1, in Alder & Hancock (1845 – 1855). The drawing shows the structure more clearly than most photographs of this translucent species with disruptive colouring.
1: substantial medial, dorsal ridge with offshoots.
2: fixed, erect rim of the mantle.
3: medial dorsal ridge on metapodium.
4: magnified inset of tubercles.