Largest mature female known is 33 cm ML from subarctic waters and carried mature eggs of 2.3 mm diameter (Kristensen, 1980). Females may mature at 70 mm ML in tropical waters. Mature males are known from 50-330 mm ML depending somewhat on latitude (Voss, et al., 1998).
Figure. Dorsal view of a young (8.7 mm ML) H. bonnellii, 37° 58'N, 27° 39' W. Drawing from Voss, 1969 (Fig. 35c).