Dinosauria — Orthomerus and Trachodon. 
23 
present day. They were implanted in partially distinct sockets, 
and a succession of teeth always growing up from beneath 
replaced the worn-down stumps. The teetli are curved and 
leaf -shaped, and the edges are elegantly serrated, a character 
peculiar to all the vegetable - feeding Dinosaurs, such as 
Acanthopholis , Scelidosaurus, &c. (see Woodcut, Figs. 24, 
and 2(>). 
Fig. 27. — -Left lateral aspect of skull of Jguanodon Bernissartensis (Boulenger) ; from the 
Wealden of Bernissart, Belgium (much reduced). The anterior aperture in the skull 
is the nares (nostril), the middle one the orhit, and the large posterior one, the infra 
temporal fossa. The predentary bone is seen at the extremity of the mandible 
(after Dollo). 
The genus Orthomerus (Seeley), an Iguanodont and a species 
of Megalosaurus , from the Upper Chalk of Maestricht, appear, as 
far as yet known, to be the most recent, and probably the last 
representatives in Europe in geological time of the great group 
of terrestrial Dinosaurs. Both sjdecies are founded upon a few 
long bones of limbs in the collection, and assuming them to 
have belonged to fully adult animals, their small proportions, 
when compared with those of their predecessors, probably 
indicates degeneration in an expiring race. 
In the genus Trachodon , of Leidy, all the dorsal vertebra) 
are opisthocoelous (hollow behind), with low arches, on which 
the rib- facet rises to the summit of the neural platform ; the 
centra are moderately compressed and wedge-shaped, with a 
limrnal carina. The teeth are simpler than in Jguanodon , witli 
lozenge-sliaped crowns, the inferior surface o f the root of each 
tooth being grooved for the reception of the summit of the 
tooth below. In T. cantabrigiensis the crowns of the teeth are 
relatively broader than in T. Foulki , from New Jersey (see 
Figures 28, a, b, c). 
Table-case, 
No. 8. 
Table-case, 
No. 9. 
