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.
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.
Bay V. Structure of Fishes.
The last bay (No. V) on the west side of the Central Hall is devoted to the display of the form and structure of Fishes.
The wall-case on the left side of this bay exhibits the external form of several characteristic types of Fishes, such as the Pike, Cod, Turbot, Dog-fish, and Skate, with the names of the various fins affixed. A striking specimen is the skeleton—mainly cartilaginous—of the Great Blue Shark (Carcharodon rondeletii), fig. 10, which occupies the greater portion of this case. It should be noted that, as in all Sharks and Rays, the upper jaw does not correspond with that of the higher Vertebrates; and particular attention should be devoted to the structure and arrangement of the arches supporting the gills.
In the south side of the table-case in this bay are shown a number of dissections, mounted in spirit, displaying the different types of skeletal structure presented by the fins in various groups of Fishes. One of the most remarkable of these types occurs in Ceratodus forsteri, the Queensland Lung-fish, in which the skeleton of the fin consists of a central jointed rod, from each side of which diverge narrower jointed rods. Alongside are specimens showing special modifications of certain fins, as in the Flying Fish ([fig. 11]) and Flying Gurnard ([fig. 12]), for the purpose of sustaining the body in the air, or, as in Pentanemus, to serve as organs of touch. Specimens of the West Indian Goby and the Lump-Sucker show modifications of the pelvic fins in connection with a sucker on the lower surface of the body; while other preparations display the pectoral (Doras) and pelvic fins (Monocentris) reduced to the condition of saw-like spines.
The structure of the skull of Fishes is illustrated in another part of the same side of this case. From this the visitor may learn how the primitive cartilaginous skull of the Sharks ([fig. 10]), Rays, Chimæras, and Lung-fishes has been gradually modified, by the addition of superficial sheathing-bones, into the bony skull of modern Fishes, such as the Cod and Perch.