CHAPTER VI. 
The Remaining Groups of Reptiles,— Orders Ichthyopterygia, 
Rhynchocephalia, and Anomodontia. 
Of the three orders remaining for consideration, two are completely extinct, and 
not known from deposits of later date than those of the Secondary period, while 
the third is represented at the present day only by a single species from New 
Zealand, although in former geological epochs it appears to have been abundant. 
The first of the three for consideration is the group of 
Fish-Lizards, —Order Ichthyopterygia. 
More or less familiar to all from the beautifully preserved skeletons obtained 
from the Lias of England and the Continent, specimens of which are exhibited in 
almost every museum, the Fish-lizards, or Ichthyosaurs, were large marine reptiles, 
with the naked body thick and whale-like, the neck extremely short, and the limbs 
modified into paddles differing from those of all other members of the class in the 
structure of their skeleton. The skull is produced into a long snout, generally 
furnished with a full series of sharp teeth, and mainly formed in the upper jaw by the 
premaxillary, or front jawbones; and the nostrils are consequently placed close to 
the eyes, the latter, like those of birds, being provided with a ring of movable plates. 
Superiorly, the skull has a hole or foramen, in the parietal bones ; while posteriorly 
the upper and lower arches are connected behind the socket of the eye by a bone 
known as the supratemporal, so that this portion of the skull is completely roofed 
over, as we shall see to be the case in the Labyrinthodont Amphibians. Then, 
again, the quadrate-bone, with which the lower jaw articulates, is firmly united to 
the adjacent elements of the skull; while in the general relations of this bone 
and the bones of the palate there is a marked agreement with the beaked reptiles. 
The teeth are confined to the edges of the jaws, where they are implanted in 
distinct sockets; and generally have conical and fluted crowns, although more 
rarely they are compressed and smooth, with sharp cutting edges at the front and 
back. The back-bone presents a nearly similar structure, the vertebrae, as shown 
in the figure on p. 6, being short discs, which may be either deeply cupped or 
nearly flat at the two ends. In the body and neck these vertebrae carry a pair of 
tubercles on each side for the articulation of the forked ends of the ribs; but in 
the tail there is but one such tubercle, the ribs being single-headed. Moreover, the 
vertebrae are further remarkable for the absence of any body union between the 
body or centrum (the part represented in the figure), and the arch enclosing the 
spinal marrow, so that these two portions are always found detached. The bones 
