The suspensorium, which forms the articulation between the cranium and the lower jaw, is T shaped; and consists of cartilage covered by bone. Of the three arms of the T the anterior has a free pointed extremity (Fig. 14 t¹) at the postero-lateral margin of the temporo-orbital fossa: it forms a true processus zygomaticus, and is bound to the upper jaw by ligaments. In R. temporaria it is comparatively much shorter than in R. esculenta. The posterior upper arm (t²) articulates with the prootic bone: the third or lower arm (t³), supported by a cartilage‍30, runs backwards and downwards to unite with the side of the broad hinder extremity of the quadrato-jugal bone.

The cartilaginous basis‍30 of the suspensorium (Fig. 17 sp, sp′) is a direct continuation of the cartilaginous basis of the cranium, and proceeds from it to the outer extremity of the prootic; from this point the cartilage runs backwards and divides into two branches; of these, one (sp′) retains the original course backwards and outwards towards the articulation of the lower jaw, and in conjunction with the quadrato-jugal (j) forms this joint. The other (sp″) is directed forwards along the anterior arm of the pterygoid bone; it widens in front (sn), and becomes directly continuous with the cartilaginous strut described above as projecting from the hinder part of the cartilaginous olfactory capsule.

8. The quadrato-jugal bones, ossa jugalia, Cuvier (Figs. 10, 17, 19 j).

This is a small process of bone, likened by Dugès to a comma, which rests by its posterior broader extremity on the cartilage of the mandibular arch‍30, and forms with it a portion of the articular head for the lower jaw. The anterior extremity is pointed, directed forwards, and attached by ligament to the maxillary bone.

9. The pterygoid bones, ossa pterygoidea (Figs. 10, 11, 17, 19 pt).

These bones, shaped like the Greek letter λ, possess each three arms: of these the middle one is attached to the under surface of the prootic bone by a cartilaginous process (Fig. 18 sp); the hinder grooved arm lies upon the under surface of the cartilaginous suspensorial arch (Fig. 18 sp′); and the anterior arm (pt) runs forwards along the inner border of the anterior ramus of the suspensorium (sp″), in contact with the maxillary, palatine, and nasal bones.

The cartilage just mentioned, by means of which the middle arm of the pterygoid is connected with the cranium (compare Fig. 18), proceeds from the cranial origin of the cartilaginous arch (sp), turns downwards and then forms a sort of articular head (cpt), which is articulated to an oval flat elevation of the prootic cartilage by a movable joint. Externally the articular head curves somewhat abruptly into the bony substance (Fig. 18 pt) of the pterygoid bone.

10. The maxillary bones, ossa maxillaria superiora, Cuvier (Figs. 10, 11, 17, 19 m).

These are elongated, curved bones, narrower behind, broader in front, and forming with the quadrato-jugals the bony support of the face. The superior surface is convex and directed outwards, the inferior surface is grooved and bears teeth along the outer edge of this groove. From the upper and inner border of the anterior half of this bone a process (processus frontalis) passes upwards, which articulates with the nasal bone. The anterior extremity of the bone articulates with the premaxillary bone, the posterior with the quadrato-jugal.

The maxillary bone articulates at its anterior end (Fig. 19 n″) with a process of the cartilaginous capsule of the nose. The broad plate of cartilage (Fig. 19 n), under cover of the processus frontalis, connects the hindermost transverse portion of the nasal cartilage with the cartilage which runs forwards from the suspensorium upon the anterior arm of the pterygoid.

11. The nasal bones, ossa fronto-nasalia, Dugès (Figs. 10, 17 fn).

These flat, triangular bones, which rest upon the nasal cartilages (n), assist to bound the orbital cavities in front, and are connected by their external angles with the maxillary bone on either side‍31.

12. The premaxillary bones, ossa intermaxillaria (Figs. 10, 11, 17, 19 i).

These two bones are united in the middle line: each consists of a tooth-supporting portion, which completes the maxillary arch, and an ascending process, to the apex of which the nasal cartilage is articulated by a movable joint (an). As muscles are attached to this process, it becomes a lever, by which movements are effected.

13. The palatine bones, ossa palatina (Figs. 19, 20 pl).

Are two transverse bony bars, situated under the anterior portion of the sphenethmoid bone on either side: each extends outwards from the apex of the parasphenoid to the maxillary bone, where this gives off its ascending process to the nasal bone.

14. The vomers, vomer (Figs. 19, 20 v).

A pair of flat bones, placed horizontally on the under surface of the cartilaginous nasal capsule in the triangular space between the palatine bone and the anterior portion of the arch of the jaw. They limit the outer border of the floor of this capsule, which lies in a groove on the dorsal surface of the bone. The outer border of each bone has three processes, and between them two notches; the hinder of these notches bounding the posterior nares. The inner borders of the two bones touch, and the under surface of each bears a transverse row of small, pointed teeth.

15. The mandible, maxilla inferior (Fig. 21).

The mandible consists of two bony arches united by ligament in the middle line, and each formed of four pieces. These are, (1) the angulosplenial, a strong, bony piece (Fig. 21 C, B1, A1), which forms the inferior and internal part of the lower jaw; below, it extends posteriorly, as far as the articulation; in front, it is attached to the dentary. In the greater part of its length it has a groove directed upwards and outwards (C, b), and above has a process which represents the processus coronoideus: (2) the dentary (A 2, B 2), a bony lamella which rests on the outer surface of the anterior half of the angulosplenial, and articulates in front with Meckel‘s cartilage; it is a thin, flat lamella of bone; (3) in the groove of the angulosplenial is found a cartilage occupying its entire length (A 4, B 4), Meckel’s cartilage; it is broader behind, and here forms the articular fossa of the lower jaw; anteriorly it is covered by the dentary, and articulates with the (4) mentomeckelian (A 3, B 3) at its anterior end, which is bound to its fellow of the opposite side by ligaments, and unites the two halves of the lower jaw.

The upper part of Meckel’s cartilage, which forms the joint with the suspensorium, must be regarded as the articulare; to this also belongs the anterior, ossified portion of the mentomeckelian‍32; the dentary, which covers Meckel’s cartilage, must represent the os dentale‍33; the first and largest bone, the angulosplenial, which lies on the inner side of the cartilage, must be considered as the os operculo-angulare, Dugès, for it contains the elements of these bones.

16. The hyoid bone, os hyoideum (Fig. 22).

This consists of a broad, thin, cartilaginous plate, with processes passing from it as represented in the figure. We distinguish in it:—(a) the body (H), somewhat oblong, and wider in front than behind. From the anterior angles there projects on either side a blunt rounded process (h); from either posterior angle a more pointed process (h′). (b) The anterior cornua (H′) (cornua styloidea) project from the anterior border of the body, first in a forward direction, then in a curve backwards and upwards (compare Fig. 12), to unite with the cartilage of the prootic bone. Where the direction of these cornua is changed each sends off a short blunt process. (c) The posterior cornua (cornua thyroidea) (H″) are bony rods which run from the hinder margin of the body, diverge posteriorly, and enclose the larynx.