256 Transactions of the 



the compound, metamorphosed cartilage. Antero-inferiorly, its edge 

 is further selvagedbya sickle-shaped " palatine " (pa.), and beneath 

 a large " pterygoid " bony plate appears (Fig. 2, pg.), which just 

 peeps from under the edge behind to the outer side (Fig. 1, pg.). 

 Farther outwards, a strong, arched bar of bone runs from the fore- 

 part of the palatine territory to the outer face of the quadrate 

 hinge ; this is the " maxillary " (Figs. 1 and 2, mx.) ; it is quite 

 normal in shape, and bows outwards so as to leave space for mus- 

 cular bands. Contrary to rule, it binds strongly on to the quad- 

 rate, its posterior end doing duty for quadrato-jugal — a bone I 

 have never seen in Fishes. But the "jugal" or malar is not 

 uncommon in Osseous Fishes, and here it is in the Sturgeon, sitting 

 bolt-upright on the end of the maxillary. The rounded condyle 

 formed by the quadrate (Figs. 1 and 2, q.) is received into a 

 scooped joint on the rest of the mandibular arch — the " articulo- 

 Meckelian " bar, or mandible proper. 



This massive, somewhat compressed rod has a large angular 

 process (Figs. 1 and 3, ag.) ; a " dentary " bone (d) has been 

 formed on its outside, and it has turned over the top of the bar to 

 clamp the inner face to some degree (Fig. 3, d. m~k.). 



In the adult (Fig. 5), which may be well studied in the fine new 

 preparation which Professor Flower has put into the museum of the 

 College of Surgeons,* the "palatines," " maxillaries," and "malars" 

 have not altered much ; the " metapterygoid " lozenge keeps free 

 from bony matter, but the huge "pterygoid" plates (pg.) have 

 grown over half the upper surface from the inner edge. A sub- 

 oval bone in front of that tract has appeared, which is at once seen 

 to be the familiar " meso-pterygoid " (ms. pg.) A plate of bone 

 behind the great "dentary" splints the angle, and is the "os 

 angulare" (Fig. 5, ag.). Antero-internally there is a "splenial" 

 plate, and on the left side a rare bony nodule, the "mento-Meckelian," 

 (m. nik.), is seen. This is described in my paper on the Frog's 

 Skull,t and is also shown to be an element in the lower jaw of man 

 by Mr. Calender.} It is very remarkable that in the tailless 

 Batrachia, and down here amongst the lower ganoids, a bone should 

 turn up which goes to form our especially human chin, which part, 

 if it had not projected, would have left us with very foolish-looking 

 faces. Hitherto, these three types are the only ones that I know of 

 as possessing a special chin-bone. 



The hyoid arch, or arch of the tongue, is immense, and is 

 chopped up into five pieces on each side. Moreover, these elements 

 are in a very different position from what they occupied at first ; and 

 if I had not watched the shuffling of these pieces in the Salmon I 



* The solid cartilage in that invaluable preparation has been ingeniously 

 imitated by wood; the cartilage itself, in drying, shrinks so as to spoil the form 

 of the preparation. 



t 'Phil. Trans.,' 1869, Plates 8 and 9, ' M. Mk.,' pp. 171 and 183. 



% ' Phil. Trans.,' I860, Plate 13, Figs. 6 and 7, p. 170. 



