OF HYPSILOPHODOX FOXII. 
1043 
pitah. The divided frontal is another Lacertilian trait: in Crocodilians the primitive 
division of the frontal disappears before the young leaves the shell.* The form and 
proportions of the nasals, and the prolongation of their anterior angles as an external 
and an internal narial process are imitated in some extant Lizards, but not, I think, in 
any Crocodilians. The division of the anterior nares and its method, as in Megalo- 
saurus, are also Lacertilian features ; the septum nasi mainly cousists of the ascending 
median prsemaxillary processes. (closely imitated in Hatteria, in which the prae- 
maxilla is paired; confluent in other Lizards where the primitive separateness of the 
prsemaxillse is early lost) which scarcely exist in Crocodilians in which the bony septum 
of the external nostril, when present, consists almost exclusively of the intruded 
tapering anterior ends of the nasal bones. The exclusion of the maxilla from the outer 
boundary of the external nostril, cited by R. Owen as a Crocodilian character,! is 
perhaps apparent and not real, because the maxilla does not cease at the posterior 
margin of the external ascending prsemaxillary process, but it is prolonged forwards 
beneath this and would become visible in very close proximity to the outer and lower 
part of the nostril if this process were removed. The lower temporal bar, a Crocodilian 
feature, is present in Iguanodon Mantelli, in the Liassic Scelidosaurus, and one extant 
Lizard— Hatteria. The fixity of the quadrate, another Crocodilian trait, is not 
attained by its being wedged in between the skull-bones, as in Crocodiles, but is due 
to the form of the squamosal articulation and the presence of the lower temporal bar. 
The anterior position of the palato-nares; the form, proportions, and connexions of the 
pterygo-palatine bars; and the median cleft in the palate are all Lacertilian characters 
not present in Crocodiles. The occurrence of teeth in the praemaxilla of simpler form 
than those in the maxilla and mandible, and the smaller size and minor complexity of 
the crown of a small number of the foremost teeth of the maxillary and mandibular 
series are highly interesting as foreshadowing the divisions of the teeth in higher 
Vertebrates. In form, in attachment, and in their mode of succession, the maxillary 
and mandibular teeth resemble those of Lizards, and not those of Crocodiles. 
Vertebral column. —No remains have yet been recovered which demonstrate the 
exact number of vertebrae in the prae- and post-sacral segments of the column. The 
sacrum certainly comprises five vertebrae. 
Professor R. Owen, in his account of “Part of the Skeleton of a Young Iguanodon 
(/. Mantelli), preserved in the British Museum, Cat. No. 39,460, suggests that the 
most anterior of a continuous chain of seventeen praesacral vertebrae corresponds to the 
fourth cervical vertebra of an Alligator. 
Professor Huxley, referring to the same vertebra, finding its capitular process in 
the level of the neuro-central suture, as in the eighth cervical vertebra of a Crocodile, 
* Miall, ‘ Skull of the Crocodile,’ p. 32. 
t Owen, R., “ Fossil Reptilia of the Weal den Dinosaurus, Iguanodon Supplement 5, p. 6. 
t Owen, R., “Monograph on the Fossil Reptilia of the Wealden Formation,” Pal. Soc., vol. for 
1855, p. 2, t. 1. 
