輻鰩

Description. The eggcase of A. radiata (Figure 2 b) is generally small. Excluding the large aberrant specimen from Borth, the mean total eggcase length is 101.2 ± 10.6 mm (range = 72.2 – 129.0), and eggcase length is 34.2 ± 1.1 mm (range = 32.7 – 36.7 mm) without horns. Eggcase width is 32.8 ± 2.6 mm (25.6 – 36.7 mm). The length and width of eggcases from historical museum specimens (n = 5) were within the size ranges recorded in contemporary samples. The dorsal surface is strongly convex and, when newly laid, covered in a thin fibrous layer. The ventral surface is slightly convex in shape but much flatter in comparison to the dorsal surface. Both capsule surfaces have longitudinal striations and latitudinal ridges that give a distinctive texture and pattern (Figure 3 a), ranging from a delicate lattice appearance to a fine rippled effect. Lateral keels (which are often damaged or lost in older specimens) run the length of the capsule from the base of the anterior horns to the base of the posterior horns, and represent an average of 17 % of the total capsule width. The anterior apron is straight while the posterior apron is much shallower and concave. The anterior horns taper to form fine, filamentous tubes while the posterior horns terminate in hooks.