skull which has become "autostylic" in order to form a rigid support for the skeleton of the buccal funnel; the styloid processes and cornual cartilages to the hyoid arch; while the relations of the posterior lateral cartilages to the subocular arches suggest that they may possibly be regarded as Meckelian cartilages which have lost their primitive function of forming biting jaws. In the median line below, and projecting backward for some distance beneath the branchial canal, there is a long and stout _lingual_ cartilage, carrying a small median and a still smaller pair of lateral cartilages at its anterior extremity, where it supports the lingual teeth and projects into the buccal funnel beneath the mouth. In front of the lingual cartilage, and connected by fibrous tissue with the inferior and hinder margin of the _annular_ cartilage, there is a median T-shaped element, the _median ventral_ cartilage. It has been conjectured that the lingual cartilage is a free basi-hyal element, and the median ventral cartilage the equivalent, elsewhere unknown, of the corresponding element of the mandibular arch.[193] {219}The remaining anterior skull elements are principally skeletal supports for the roof and walls of the buccal funnel. The roof is supported by an extended _anterior dorsal_ cartilage, which is overlapped behind by the ethmoid cartilage, while the circular margin of the funnel is strengthened by a large ring-like _annular_ cartilage. On each side of the latter there is a slender, rod-like, _styloid_ cartilage, and above the latter a small _anterior lateral_ cartilage. All these cartilages are usually termed labial cartilages, and it is at least possible that they possess representatives in the similarly named structures of the Dog-Fish and the larvae of some of the tailless Amphibia. It must not be forgotten, however, that the annular cartilage bears some resemblance to the ring of cartilage which encircles the lips of the buccal cavity in Amphioxus. The complex supporting skeleton of the gill-sacs forms a basket-like structure. It consists on each side of nine unsegmented, irregularly curved, and slightly branched cartilaginous rods, situated in the outer margins of the inter-branchial septa, directly internal to the skin. The first lies directly behind the styloid process (hyoid arch), the second and third in front of and behind the first gill-sac, and of the remainder one lies just behind each of the six succeeding gill-openings; above and below each gill-aperture the rods are connected by longitudinal bars, and also in the median ventral line by a pair of similar partially united bars. The dorsal ends of the rods are also connected on each side by another longitudinal bar, which runs alongside the notochord and in front blends with the chondrocranium. The rods forming the last pair are continuous with a cup-like cartilage, supporting the lateral and hinder walls of the pericardium.