Fig. 53.—Comparison of Cartilaginous Skeleton of Limulus and Ammocœtes. A, Diagram of cartilaginous skeleton of Limulus. "Soft cartilage", entapophysial ligaments, deep black; branchial bars simply hatched; "hard cartilage", lateral trabeculæ of entosternite, netted; "Ph.", position of pharynx. B, Diagram of cartilaginous skeleton of Ammocœtes. "Soft cartilage", sub-chordal cartilaginous bands, deep black; branchial basket-work (first formed part), simply hatched; "hard cartilage", cranio-facial skeleton, trabeculæ, parachordals and auditory capsules, netted; "Inf.", position of tube of infundibulum (old œsophagus).