(3) Visceral arches. The first of the visceral arches is much larger and heavier than the rest. It is known as the _hyoid arch_. Each side of the arch consists of two rods of cartilage: (1) the _hyomandibular cartilage_, which articulates with a distinct facet on the lateral surface of the auditory capsule, and extends from here downward, outward, and backward; (2) the _ceratohyal_ cartilage, which is movably articulated to the hyomandibular and extends downward, forward and inward. The ventral ends of the ceratohyals are united by a median, plate-like _basihyal_. The palato-quadrate and Meckelian cartilages are suspended from the hyomandibular by several strong ligaments, the direct attachments of the jaws to the cranium being of soft connective tissue only. Both the hyomandibular and ceratohyal cartilages bear slender rods (_branchial rays_) on their posterior edges, which support the anterior wall of the first gill pouch. Note the position of the spiracle between the mandibular and hyoid arches. The anterior wall of the spiracle is strengthened by two small, flat, vertical cartilages, probably homologous with the branchial rays of the gill arches. The remaining five visceral arches differ little in their construction. Dorsally, each has a flat, sickle-shaped _pharyngo-branchial_ cartilage attached to the vertebral column by fibrous bands. The pharyngo-branchials of the last two arches are fused. Ventrad to each pharyngo-branchial is an _epibranchial_ cartilage. The next segment of each arch is formed by the _ceratobranchial_ cartilage. All the epibranchials and ceratobranchials except those of the fifth arch bear slender branchial rays. The ventral ends of the ceratobranchials articulate with each other, the first being attached to the ceratohyal by ligament. The second, third, and fourth arches have another more ventral series of cartilages, the _hypobranchials_. The lower ends of the hypobranchials are attached to a large median plate, the _basibranchial_. The fourth ceratobranchial joins the third hypobranchial, while the ceratobranchials of the fifth arch are attached to the basibranchial directly. The basibranchial is composed of two segments closely united by ligament; the anterior one narrow, the posterior broad and flat in front, tapering to a sharp point behind. Short teeth of cartilage, called gill rakers, project into the pharynx from the inner edges of the arches. A dorsal and a ventral series of _extra-branchial_ cartilages, thin, slender plates, lie on the external side of each gill arch.