- Comparison of the sixth prosomatic limb of a recent scorpion (B), of Palaeophonus (C), and of Limulus (A), showing their agreement in the number of segments; in the existence of a movable spine, Sp, at the distal border of the fifth segment; in the correspondence of the two claws at the free end of the limb of Scorpio with two spines similarly placed in Limulus; and, lastly, in the correspondence of the three talon-like spines carried on the distal margin of segment six of recent scorpions with the four larger but similarly situated spines on the leg of Limulus; s, groove dividing the ankylosed segments 4 and 5 of the Limulus leg into two.
7) - thus six in all (as in some Crustacea), including prosthomeres, all ankylosed by their terga to form a cephalic shield.
The horizontal ramus, long, straight, and compressed, gradually narrows towards the symphysis, where it expands laterally to form with the ankylosed opposite ramus the wide, semicircular, shallow alveolar border for the incisor teeth.
A few frogs have the skin of the back studded with stellate bony deposits Phyllomedusa, Nototrema), whilst two genera are remarkable for possessing a bony dorsal shield, free from the vertebrae (Ceratorphrys) or ankylosed to them (Brachycephalus).
The teeth are not implanted in sockets, but become ankylosed with the .ttr c bones that bear them, and are replaced by FIG.