DR. GUNTHER ON THE ANATOMY OE HATTERIA. 
608 
ends of the premaxillaries dilated teeth anchylosed to the bone as in Hatteria \ And 
even if they really be part of the bone itself, the step from the premaxillary dentition 
of Hatteria to this beak of Bhynchosaurus can scarcely be regarded as greater than that 
from the dentition of the young Hatteria to that of the fully developed. However, 
a real affinity between the recent Lizards mentioned and Bhynchosaurus can only be con- 
jectured, as its toothless lateral alveolar edges have been seen in one specimen only ; 
nothing is known of the palate, or of the arrangement of the bones in the temporal 
region ; its orbit is complete. 
It will be a point of great interest to know whether those extinct Saurians which are 
distinguished either by entirely edentulous jaws, or by a combination of teeth with an 
edentulous and cutting alveolar edge ( Cryp to dontia and Dicynodontia of Owen), are 
completely toothed when young. This does not appear to be at all improbable ; and if 
it should prove to be the case, the transition from the normal Saurian dentition to that 
of the Turtle will be complete*. Among Fishes the family of Labridce offers a 
strikingly similar series of forms of dentition ; and the* observations made on Hatteria 
and Uromastyx go far to prove the correctness of the views advocated in the ‘ Catalogue 
of Fishes,’ vol. i.v, viz. that small fishes with complete dentition (referred by other 
authors to different species and genera) are merely the young of others with partly 
edentulous jaws, and that the Scaroid and Odacoid fishes cannot be separated from the 
Labroids on account of their dentition. Thus in this most natural family we find the 
majority of generic forms provided with a normal complete dentition ; in others ( Chcerops , 
Xiphochilus , Pseudodax , See.) the lateral teeth are gradually and normally replaced by a 
more or less cutting edge of the mandible ; and finally, in the Scarina and Odacina the 
entire mass of the teeth and jaws are coalesced, forming a beak with sharp cutting edges, 
the single teeth being still visible in the true Scarus , whilst they have entirely disap- 
peared in adult Pseudoscarus and Odax. Unfortunately, up to this time, we are unac- 
quainted with the dentition of very young Scaroid fishes. 
All Lizards masticate their food in some degree ; in so doing their lower jaw is moved, 
in a vertical direction only, towards the upper. In full-grown specimens of Hatteria 
a great portion of the side of the jaws has a sharp cutting edge, whilst the toothed portion 
also has more the appearance of a cutting serrated edge than of series of teeth. The 
force in cutting and sawing is, of course, considerably increased by the property of 
moving the lower jaw backwards and forwards, a property dependent on the peculiarity 
of the maxillary joint as described above. 
All the specimens examined had the stomach and upper part of the intestine empty ; 
but the rectum of one contained a great mass of the remains of the young of some bird 
which probably builds on the ground ; the plumes of the feathers without quills (which 
being still soft had been digested), together with the condition of the bills and bones, 
could not leave any doubt as to the age of the bird. The same mass contained also one 
fragment of the elytron of a beetle. It is known, from actual observation of living speci- 
* The embryo of Trionyx shows numerous rudiments of teeth. — Owen, Odontography, p. 179. 
MDCCCLXVII. 4 N 
