AND CLASSIFICATION OF THE FOSSIL REPTILIA. 
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extremities. The form of the pterygoid bone is quite as much like Ichthyosaurus 
as Plesiosaurus. But, though the superficial resemblance is more obvious with 
Ichthyosaurus, I believe the resemblances with Plesiosaurus are the more important. 
A certain resemblance may be considered to be shown by the Triassic Crocodile 
Belodon ; but that type, which lias the orbits placed far back, has large ant-orbital 
vacuities, above which the external nares are situate ; the nasal bones are exceedingly 
small and short; and the pterygoid bones which meet in the median line do not 
extend so far back as in Protorosaurus. 
In none of the types with which comparison has been made are teeth ever present 
on the bones of the palate. The existing groups of Reptiles in which this character 
is seen are Ophidia, Lacertilia, and Rhynchocephalia, in all of which orders the 
external nares are terminal or sub-terminal. The same relation characterises the extinct 
Reptiles which have teeth on the bones of the palate, such as Hype rod apedon and 
Phynchosaurus; and therefore, if as close a general resemblance should exist between 
such types and Protorosaurus, as the Nothosaurs have shown, the probabilities will 
incline to the anterior nares having been terminal. Phynchosaurus apparently has 
teeth on both the palatine and pterygoid bones ; the pterygoid is firmly united to the 
quadrate, the palate is open in the median line, but there is seemingly no very close 
resemblance to Protorosaurus in the forms of the bones. The upper surface of the 
skull is fairly comparable in contour, in the relative positions of the vacuities, in the 
broad, flat, frontal region, and in the existence of a parieto-frontal crest formed by the 
temporal muscles. The brain-case, however, in Phynchosaurus appears to be distinct 
from the roof bones of the head, as in Procolophon and some Lizards ; and this condition 
has no parallel in Protorosaurus. No existing Reptile, so far as I am aware, has teeth 
on the vomer ; and this toothed condition of all the bones of the palate prevents detailed 
comparison being made with Lizards or Rhynchocephalia. The character, so common 
among Fishes and extinct Amphibia, is the more remarkable as a comparatively 
isolated resemblance to lower types. Besides its terminal pair of tusk-like incisors, 
Phynchosaurus has apparently two parallel rows of teeth upon the palatal plate of 
the maxillary, and two short parallel longitudinal rows in the hinder part of the 
palate, which appear to be upon the pterygoid, or pterygoid and vomerine bones, for 
no separation can be made out with certainty between the bones of the palate. In 
Phynchosaurus the malar bones are produced downward and backward so as partly to 
overlap the lower jaw, as in Parieasaurus, a character of which Protorosaurus gives no 
indication. Rhynchosaurus has the post-fronto-squamosal arch strongly developed, of 
which no trace is preserved in the Protorosaurus. 
The condition of the teeth, anchylosed to the palate, with corresponding cavities in 
the positions where fangs would usually be, is a remarkable peculiarity, which needs 
further elucidation. The teeth are anchylosed to the jaw in Labyrinthodonts ; but 
I know of no such union or such sub-dental loculi among Reptiles as are here seen. 
The cavities may have remained after the teeth emerged from them by absorption of 
