42 
So far as the skull structure is concerned, I see no reason for not 
regarding Parasaurolophus to be a true member of the Lambeosaurin®. 
In fact the whole skeletal structure, except the relative proportions of the 
fore limb bones, is in accord with such an assignment. The short skull 
(exclusive of crest), strongly decurved edentulous portion of the mandible, 
short quadrate, and roofed narial passages are typical Lambeosaurid 
features, and strikingly unlike the high, long-headed, long-beaked skulls 
of the Saurolophin® to which it was originally assigned. In view of these 
facts I now propose its removal to the sub-family Lambeosaurin®. 
Brain Case 
“In the brain-case of the skull Stephanosaurus [. Lambeosaurus ] type 
the sutures can be readily traced between the presphenoid and orbito- 
sphenoid and between the orbitosphenoid and alisphenoid. Also the 
suture between the alisphenoid and the basisphenoid is preserved, proving 
by its position that the large flange, directed outward from above and 
somewhat behind the basisphenoid process, belongs to and is part of the 
basisphenoid. It may be of interest, also, to note that in this skull the 
ophthalmic branch of the trigeminal nerve (V) is enclosed in bone in its 
forward course and does not occupy an open channel as it appears to do in 
Edmontosaurus. Further, indicating an unusually perfect preservation of 
structural detail, the separation of the fenestra rotunda from the fenestra 
ovalis by an horizontal bar of bone is excellently shown.” 
The prootic, which is always pierced by foramen VII for the exit 
of the facial nerve, may also be partly differentiated. The suture 
between it and the opisthotic may be traced from the fenestra ovalis as 
running slightly upward, outward, and backward and thence turning 
forward and upward to the nearly horizontal parietal contact. The 
foramen ovale (V) is especially large, and it is quite apparent that its 
boundaries lie largely within the prootic, the alisphenoid forming only the 
anterior boundary, as in Saurolophus, Camptosaurus, and the dinosauria 
generally. 
Mandible 
The complete lower mandible in Lambeosaurus lambei consists of the 
dentary, surangular, angular, articular, prearticular, which are all paired 
bones, and the single predentary. These are all present in the type, 
(Plate VI), and in a beautiful state of preservation. The splenial 
appears to be absent in all members of the Hadrosaurid®. The element 
which has been identified by Lambe and others as splenial is the prearticular. 
It borders as usual the upper inner margin of the posterior meckelian fossa, 
is in contact posteriorly with the articular, and continues forward as a 
nearly vertical plate to meet the dentary. At the anterior end it curves 
outwardly over the pointed supero-internal termination of the dentary 
behind the magazine, and continues forward as a rapidly narrowing process 
that ends in a point beneath the hindermost part of the dental magazine. 
The tip of this bone is missing in the type, but is present in other specimens 
in the collection. It is in contact inferiorly with the angular for practically 
its entire length. It will be noted from the above description that this 
bone fulfils all the requirements of the prearticular as to position and 
