The opposite, or north, side of the table-case displays the different modifications of the skull and teeth of living and extinct Reptiles. In some, like Crocodiles and Ichthyosaurs, the jaws are armed with a full series of sharply pointed teeth, while in others, like the Tortoises and Turtles, they are devoid of teeth and encased in horn. Very remarkable is the approximation to a carnivorous mammalian type presented by the dentition of some of the extinct mammal-like Reptiles, or Theromorphs, and equally noticeable are the palatal crushing teeth of certain other extinct Reptiles known as _Placodus_ and _Cyamodus_. The peculiar dentition of the New Zealand Tuatera, and likewise that of its extinct European and Indian ally _Hyperodapedon_ (fig. 9), are also shown. [Illustration: FIG. 9.--SKULL OF THE GIANT TUATERA (_Hyperodapedon gordoni_), from the Triassic Sandstone of Lossiemouth, Elgin, (¼ nat. size). A, upper surface of skull; B, palatal aspect of skull; C, under side of front of lower jaw; _Pmx_, premaxillary bone; _Mx_, maxillary; _Pl_, palatal teeth; _Md_, lower jaw; _O_, orbit, or eye-socket; _N_, nostrils; _S_, temporal pit; _S’_, lateral temporal fossa. ] The brain and other internal organs of Reptiles are displayed in the left half of the wall-case on the north side of this bay, in which are also shown the eggs of many species, in some cases with the embryo. [Illustration: FIG. 10.--SKELETON OF THE GREAT BLUE SHARK (_Carcharodon rondeletii_), with portion of backbone on a large scale. _pl_, functional upper jaw, and _su_, its reflected portion; _md_, lower jaw; _hy_, ceratohyal; _br_, branchial arches; _co_, pectoral girdle; _ph_, cartilaginous portion of pectoral, or front paired fin; _r_, dermal portion of pectoral fin; _pu_, pelvic, or hind paired, fin; _c_, centra, or bodies, of the vertebræ; _na_, neural, or upper, and _ha_, hæmal, or lower, arch. The median fins are not lettered. ] In the right half of the same case are exhibited a number of preparations showing the external form and internal structure of Frogs and Salamanders, or Amphibians, living and extinct. The Giant Salamander of Japan (_Megalobatrachus_ or _Cryptobranchus_) is represented by a stuffed specimen; but the Newts, Salamanders, and Frogs are shown in spirit. Very curious is the almost colourless and blind Olm (_Proteus_) from the caves of Carniola; as also are the so-called Cœcilians, or Apoda, which have the habits and, in some degree, the appearance of large worms. Special specimens exhibit the structure of the extinct Labyrinthodonts, in which the hinder half of the skull is completely roofed over by bone; while the teeth in many instances exhibit a curious in-folded arrangement from which the group derives its name. [Sidenote: Bay V. Structure of Fishes.]